diff options
| author | Ingo Molnar <mingo@kernel.org> | 2026-10-07 18:25:55 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2026-10-07 18:25:56 +0200 |
| commit | 3be71701f785587f115eed063cbb148d9d577b95 (patch) | |
| tree | 3ae7f72b34cb6cd046e4373beb03ff8c1c910c87 | |
| parent | 959fd5e1c34667dd68c02fa5bad44bacca9b0acf (diff) | |
| parent | 4a3b51aab6e25244d97936aa65e6d5425adf98e1 (diff) | |
| download | linux-next-3be71701f785587f115eed063cbb148d9d577b95.tar.gz linux-next-3be71701f785587f115eed063cbb148d9d577b95.zip | |
Merge branch into tip/master: 'sched/core'
# New commits in sched/core:
4a3b51aab6e2 ("smpboot: Don't park the thread if work is pending")
40dcc9bdbef3 ("irq_work: Flush lazy work CPU down on PREEMPT_RT")
791b1760accd ("irq_work: Update a comment regarding CPU hotplug invocation")
648d44bda731 ("sched/topology: Add asymmetric SMT packing override")
c8fc4136fd3c ("sched/fair: Honor asymmetric SMT priority in idle selection")
53bc5c556b82 ("sched: Set TIF_NEED_RESCHED before calling __trace_set_need_resched()")
4b1f75be23c4 ("sched/core: Fix context analysis errors in non-preferred CPU push")
1fb28c664a19 ("virt/steal_governor: Enable the driver")
27d47ebce4d6 ("virt/steal_governor: Implement steal_governor policy loop")
4b9302d494ff ("virt/steal_governor: Add control knobs for handling steal values")
9a8e740ee9f6 ("virt: Introduce steal governor driver")
68957caaa9c0 ("sched/debug: Add migration stats due to non preferred CPUs")
74699f56ebcf ("sched/core: Push current task from non preferred CPU")
4ee29b029058 ("sched/fair: Load balance only among preferred CPUs")
d8a3da0de843 ("sched/core: Try to use a preferred CPU in is_cpu_allowed")
620824516557 ("sysfs: Add preferred CPU file")
518b32bd5bb3 ("cpumask: Introduce cpu_preferred_mask")
06a49ef784ac ("sched/docs: Document cpu_preferred_mask and Preferred CPU concept")
cfb463b7172d ("cpumask: Introduce cpumask_intersects_and")
a8d0854a76a8 ("sched/cputime: Add kcpustat_field_total helper")
be100c77178e ("sched: Add sched_ext hooks for proxy execution")
57c75e3ae38c ("sched: Add helper to block retained proxy donors")
a49653d0abeb ("sched/core: Mark wakeups completed through ttwu_runnable()")
8f8c0417e973 ("sched/core: Dequeue waking proxy donors before reset")
313b652837d0 ("sched/core: Drop mutex locks before proxy rescheduling")
627ea30aca3b ("sched/wait: Clarify WF_SYNC wakeup semantics")
d2e010082757 ("sched/eevdf: Handle more short slice waking cases")
4bf32ec3327d ("sched/eevdf: Align update_protect_slice to set_protect_slice")
aae2a33ea662 ("sched/eevdf: Ensure that vprot will never go above a min slice")
c9ce69fc43bd ("sched/fair: Randomize equally shallow slow-path candidates")
abe440b3770f ("sched/fair: Drop idle recency from slow-path CPU selection")
fbbc63fed0b0 ("sched/core: Remove redundant core_sched_seq")
819224e506bc ("sched/fair: Remove dead code on enqueue_task_fair()")
c72945693b90 ("sched: Restart fair hrtick after same-task repicks")
a9b3c7570564 ("sched/headers: Replace __ASSEMBLY__ with __ASSEMBLER__ in the <uapi/linux/sched.h> header")
e81ee0630837 ("sched/fair: Reset NUMA fault locality after scan period update")
ef9293b3b797 ("sched: dynamic: Fix preemption model strings")
879eaa76e608 ("sched: Remove unneeded function type cast in do_balance_callbacks()")
f549101187c8 ("sched/deadline: check start_dl_timer expiry with ktime_before()")
2a672daa4b27 ("sched/feat: Use the new static key API for sched_feat")
a5576ebce920 ("sched: Convert paravirt_steal to new static key APIs")
9650ce11f2e3 ("sched: dynamic: Simplify preempt model accessors")
5b9a28eeed37 ("sched: dynamic: Remove HAVE_PREEMPT_DYNAMIC_{CALL,KEY}")
aa4178f63847 ("sched: dynamic: Simplify irqentry_exit_cond_resched()")
b9d267b9d632 ("sched: dynamic: Simplify preempt_schedule{,_notrace}()")
88e0b3bb9930 ("sched: dynamic: Simplify {cond,might}_resched()")
d3d16750693b ("sched: dynamic: Make PREEMPT_DYNAMIC depend on ARCH_HAS_PREEMPT_LAZY")
772d9ffbfd26 ("sched: Migrate whole chain in proxy_migrate_task()")
6b73a09e943f ("sched: Break out core of attach_tasks() helper into sched.h")
1f8805138593 ("sched: Switch rq->next_class in proxy_reset_donor()")
09351db90a28 ("sched/core: Don't proxy-exec unmatched cookie lock owners")
9be817f991e2 ("sched/core: Avoid migrating blocked_on tasks")
3dd95f077371 ("sched/core: Don't steal a proxy-exec donor")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
62 files changed, 1246 insertions, 594 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 82d10d556cc8..8f250b8693b8 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -806,3 +806,17 @@ Date: Nov 2022 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> Description: (RO) the list of CPUs that can be brought online. + +What: /sys/devices/system/cpu/preferred +Date: Sep 2026 +Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> +Description: + (RO) the list of preferred CPUs applicable in + paravirtualized environments. + + The steal governor driver dynamically adjusts this mask + based on observed steal time. Scheduling tasks on + CPUs outside of this list may lead to performance + degradations due to underlying physical CPU contention. + + See Documentation/scheduler/sched-paravirt.rst for more details. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index e75344f4e0cd..8157ff434cb5 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6800,6 +6800,18 @@ Kernel parameters solution to mutex-based priority inversion. Format: <bool> + sched_smt_asym_packing= [KNL,SMP] + Format: on + Force asymmetric packing at the SMT scheduling domain. + Idle CPU selection prefers siblings with a higher + arch_asym_cpu_priority(). The default implementation + prefers lower-numbered logical CPUs, but architecture + overrides remain authoritative. Equal priorities do + not establish a sibling preference. For example, x86 + with CONFIG_SCHED_MC_PRIO normally assigns the same + core priority to both SMT siblings, so this option + does not favor either sibling. + sched_verbose [KNL,EARLY] Enables verbose scheduler debug messages. schedstats= [KNL,X86] Enable or disable scheduled statistics. diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst index 6601a258690f..26b7638a327d 100644 --- a/Documentation/driver-api/index.rst +++ b/Documentation/driver-api/index.rst @@ -139,6 +139,7 @@ Subsystem-specific APIs sm501 soundwire/index spi + steal-governor surface_aggregator/index switchtec sync_file diff --git a/Documentation/driver-api/steal-governor.rst b/Documentation/driver-api/steal-governor.rst new file mode 100644 index 000000000000..3817eedb38d7 --- /dev/null +++ b/Documentation/driver-api/steal-governor.rst @@ -0,0 +1,151 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Steal Governor +============== + +:Author: Shrikanth Hegde <sshegde@linux.ibm.com> + +Introduction +============ + +The steal governor is aimed at mitigating the Noisy Neighbour problem +which occurs in paravirtualized environments with CPU overcommit. +The performance of a workload running in one VM gets degraded by +the activity of other VMs on the same host. As a result, all VMs +collectively make slower forward progress. + +In such systems, high utilization in all VMs causes the hypervisor to +frequently preempt vCPUs. This vCPU preemption is expensive. +To mitigate this, the kernel aims to restrict workloads to a subset of +Preferred CPUs to reduce physical CPU contention. +A detailed explanation of Preferred CPUs is available in +``Documentation/scheduler/sched-paravirt.rst``. + +The steal governor selects ``CONFIG_PREFERRED_CPU=y`` which enables the +scheduler core infrastructure to move the tasks to Preferred CPUs where +possible. The driver controls the policy decisions regarding the state of +preferred CPUs. That is, this driver decides which CPUs are preferred +and which CPUs are non-preferred. + +The driver code is available at ``drivers/virt/steal_governor.c``. + +Core idea +========= + +steal time is an indication available today in Guest which shows contention +for underlying physical CPU. Use it as a hint in the guest to fold the +workload to a reduced set of vCPUs. When there is contention, steal time +will show up in all the guests. When each guest honors the hint and folds +the workload to a smaller set of vCPUs (Preferred CPUs), it reduces the +contention and thereby reduces vCPU preemption. +This is achieved without any cross-guest communication. + +Steal governor driver effectively does: + +1. Periodically computes the steal ratio using accumulated steal time + across possible CPUs, normalized by the number of active CPUs. + +2. If steal ratio is greater than high threshold, reduce the number of + preferred CPUs by 1 core. Ensure at least one core is left always. + Skip changing the state of offline CPUs in that core. + +3. If steal ratio is less than or equal to low threshold, increase the + number of preferred CPUs by 1 core. If preferred is same as active, + nothing to be done. Skip changing the state of offline CPUs. + This helps to handle cases where few CPUs are offline in a core and + those offline CPUs will not be marked as preferred. + +4. Ensure preferred CPUs is always subset of active CPUs. + On feature disable it is same as active CPUs. + +This feature works best only when all the VMs enable the feature as +it is a co-operative scheme. If a specific VM doesn't enable this feature +it may end up with more CPUs than others, still should lead to better +performance when seen from system view. Those who enable this driver must +ensure it is enabled in all VMs. + +Note that this driver is strictly intended for actual guests; for example, +loading this module in a privileged VM like Xen Dom0 is blocked. + +Workload considerations +======================= + +The steal governor is useful for workloads where vCPU preemption has +costs beyond the lost CPU time, such as lock-holder preemption, critical +sections, communicating threads, and cache or TLB disruption. + +Pure CPU-time workloads with independent workers may not benefit and +could see a small regression due to additional guest scheduling overhead. + +Module Parameters +================= + +interval_ms +----------- + +How often steal governor checks for steal time. +Default: 1000 i.e. 1 second. Value should be in between 100ms to 100sec. + +This controls how fast steal governor driver reacts to changes to the +contention of physical CPUs. Since it does a fair amount of work, setting +too low may have overhead. Setting it too high might render it ineffective. + +low_threshold +------------- + +lower threshold value in percentage * 100. +Default: 200, i.e. 2% steal is considered as low threshold. +Can't be higher than high_threshold. + +This determines what values should be considered as nil/no steal values. +When steal governor sees steal ratio is less than or equal to this value, +it will increase the preferred CPUs by 1 core. +Using zero might cause oscillations. + +high_threshold +-------------- + +higher threshold value in percentage * 100 +Default: 500, i.e. 5% steal is considered as high threshold. +Can't be lower than low_threshold. Must be less than 10000. + +This determines what values should be considered as high steal values. +When steal governor sees steal ratio is higher than this value, it will +reduce the preferred CPUs by 1 core. + +Limitations of default values +----------------------------- + +Because of the vast diversity in VM configurations and different +architectures, the default thresholds may not be optimal for all systems. +Users may need to tune these parameters based on the system under +test to achieve the best results. + +The governor sums the steal time across all possible CPUs, which ensures +the accumulated steal time remains a monotonically increasing value. +However, to calculate the effective steal ratio, it divides this sum +by the number of active CPUs. Because only active CPUs contribute to +the steal time delta, this prevents threshold dilution on sparsely +populated systems. + +The driver reduces/increases preferred CPUs by core-level. This could provide +faster convergence for hypervisors such as powerVM. But on KVM and Xen +convergence could be slower depending on the configuration. +Using a smaller interval_ms could help one to expedite it. + +Reasons for CONFIG_STEAL_GOVERNOR=m +=================================== + +Selecting this driver makes CONFIG_PREFERRED_CPU=y. That makes configs +driven by user preference. Though one can have CONFIG_STEAL_GOVERNOR=y, +It is recommended to build CONFIG_STEAL_GOVERNOR=m due to below reasons: + +1. Doing periodic work has additional overheads. Enabling this driver + in systems where steal time cannot happen is of no use. There is no + benefit with additional overheads in such systems. + +2. This works well when all VMs work in a co-operative manner. When an + administrative user enables it in one VM, he/she will likely enable + it in all VMs. + +3. User can tweak the module parameters by reloading the module. diff --git a/Documentation/scheduler/index.rst b/Documentation/scheduler/index.rst index 17ce8d76befc..a43647b9706d 100644 --- a/Documentation/scheduler/index.rst +++ b/Documentation/scheduler/index.rst @@ -23,5 +23,6 @@ Scheduler sched-stats sched-ext sched-debug + sched-paravirt text_files diff --git a/Documentation/scheduler/sched-paravirt.rst b/Documentation/scheduler/sched-paravirt.rst new file mode 100644 index 000000000000..311cdbf2722b --- /dev/null +++ b/Documentation/scheduler/sched-paravirt.rst @@ -0,0 +1,67 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. _sched-paravirt: + +Preferred CPUs +============== + +In paravirtualized environments CPU overcommit is a common scenario. +i.e. the sum of virtual CPUs (vCPUs) of all VMs is greater than number of +physical CPUs (pCPUs). Under such conditions when all or many VMs have +high utilization, hypervisor won't be able to satisfy the CPU requirement +and has to context switch within or across VMs. The hypervisor needs to +preempt one vCPU to run another. This is called vCPU preemption. +This is more expensive compared to task context switch within a vCPU, since +hypervisor lacks vCPU context and could preempt a critical section which +slows forward progress. + +In such cases it is better that combined vCPU demand from all VMs is reduced +by not using some of the vCPUs in each VM. vCPUs where workload can be safely +scheduled which won't increase any contention for pCPU are called +"Preferred CPUs". + +One of the main design constructs is that preferred CPUs are always +a subset of active CPUs. In most cases preferred CPUs will be same as +active CPUs. When there is pCPU contention, Preferred CPUs will reduce +based on the steal time. When the pCPU contention goes away as indicated +by steal time, Preferred CPUs could become same as active CPUs again. +The policy decisions are to be taken by driver. +For example, steal_governor. Look at its documentation for more +details. (``drivers/virt/steal_governor.c``) + +Scheduling decisions such as wakeup, pushing the task etc, need this +CPU state info. This is maintained in ``cpu_preferred_mask``. +vCPUs which are not in ``cpu_preferred_mask`` should be treated as vCPUs which +should not be used at this moment provided it doesn't break user affinity. + +This is achieved by: + +1. Selecting a preferred CPU at wakeup using fallback mechanism. +2. Pushing the task away from non-preferred CPU at tick. +3. Selecting only preferred CPUs for load balance. + +``/sys/devices/system/cpu/preferred`` prints the current ``cpu_preferred_mask`` +in cpulist format. + +Notes: + +1. This feature is available under ``CONFIG_PREFERRED_CPU``. Driver which + makes decisions should enable it. For example, steal_governor driver + (``CONFIG_STEAL_GOVERNOR``). On enabling the driver, CPU preferred state + can change based on steal time. Without the driver, preferred CPUs is + same as active CPUs. + +2. This feature works for the FAIR class only. + +3. A pinned task, which can't be moved to preferred CPUs will continue + to run based on its affinity. But no load balancing happens if it is affined + only on non-preferred CPUs. + +4. Decision to change the preferred CPU state is driven by the kernel. + Hence it shouldn't break user affinities. One of the main reasons why + CPU hotplug or Isolated cpuset partitions was not a solution. + +5. This feature works best only when all the Guest VMs enable the feature as + it is a co-operative scheme. If a specific VM doesn't enable this feature + it may end up with more CPUs than others, still should lead to better + performance when seen from system view. + Users who enable this driver must ensure it is enabled in all Guest VMs. diff --git a/MAINTAINERS b/MAINTAINERS index 65e8a4b5c90b..2f9886865e90 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -26240,6 +26240,15 @@ F: rust/helpers/jump_label.c F: rust/kernel/generated_arch_static_branch_asm.rs.S F: rust/kernel/jump_label.rs +STEAL GOVERNOR DRIVER +M: Shrikanth Hegde <sshegde@linux.ibm.com> +R: Yury Norov <yury.norov@gmail.com> +L: linux-kernel@vger.kernel.org +S: Maintained +T: git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core +F: Documentation/driver-api/steal-governor.rst +F: drivers/virt/steal_governor.c + STI AUDIO (ASoC) DRIVERS M: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com> L: linux-sound@vger.kernel.org diff --git a/arch/Kconfig b/arch/Kconfig index 45c657772362..c0a6a13b06a1 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1712,44 +1712,6 @@ config HAVE_STATIC_CALL_INLINE depends on HAVE_STATIC_CALL select OBJTOOL -config HAVE_PREEMPT_DYNAMIC - bool - -config HAVE_PREEMPT_DYNAMIC_CALL - bool - depends on HAVE_STATIC_CALL - select HAVE_PREEMPT_DYNAMIC - help - An architecture should select this if it can handle the preemption - model being selected at boot time using static calls. - - Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a - preemption function will be patched directly. - - Where an architecture does not select HAVE_STATIC_CALL_INLINE, any - call to a preemption function will go through a trampoline, and the - trampoline will be patched. - - It is strongly advised to support inline static call to avoid any - overhead. - -config HAVE_PREEMPT_DYNAMIC_KEY - bool - depends on HAVE_ARCH_JUMP_LABEL - select HAVE_PREEMPT_DYNAMIC - help - An architecture should select this if it can handle the preemption - model being selected at boot time using static keys. - - Each preemption function will be given an early return based on a - static key. This should have slightly lower overhead than non-inline - static calls, as this effectively inlines each trampoline into the - start of its callee. This may avoid redundant work, and may - integrate better with CFI schemes. - - This will have greater overhead than using inline static calls as - the call to the preemption function cannot be entirely elided. - config ARCH_WANT_LD_ORPHAN_WARN bool help diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 8ded9566f192..cce20d87dd69 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -217,7 +217,6 @@ config ARM64 select HAVE_PERF_EVENTS_NMI if ARM64_PSEUDO_NMI select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP - select HAVE_PREEMPT_DYNAMIC_KEY select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RELIABLE_STACKTRACE select HAVE_POSIX_CPU_TIMERS_TASK_WORK diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h index 9ecc2766a9f2..e86e850e9b17 100644 --- a/arch/arm64/include/asm/preempt.h +++ b/arch/arm64/include/asm/preempt.h @@ -104,19 +104,9 @@ static inline bool should_resched(int preempt_offset) void preempt_schedule(void); void preempt_schedule_notrace(void); -#ifdef CONFIG_PREEMPT_DYNAMIC - -void dynamic_preempt_schedule(void); -#define __preempt_schedule() dynamic_preempt_schedule() -void dynamic_preempt_schedule_notrace(void); -#define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace() - -#else /* CONFIG_PREEMPT_DYNAMIC */ - #define __preempt_schedule() preempt_schedule() #define __preempt_schedule_notrace() preempt_schedule_notrace() -#endif /* CONFIG_PREEMPT_DYNAMIC */ #endif /* CONFIG_PREEMPTION */ #endif /* __ASM_PREEMPT_H */ diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c index 572efb96b23f..30bf61d031eb 100644 --- a/arch/arm64/kernel/paravirt.c +++ b/arch/arm64/kernel/paravirt.c @@ -157,9 +157,9 @@ int __init pv_time_init(void) static_call_update(pv_steal_clock, para_steal_clock); - static_key_slow_inc(¶virt_steal_enabled); + static_branch_inc(¶virt_steal_enabled); if (steal_acc) - static_key_slow_inc(¶virt_steal_rq_enabled); + static_branch_inc(¶virt_steal_rq_enabled); pr_info("using stolen time PV\n"); diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig index 2067d1f2ad7a..c346a9229542 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -170,7 +170,6 @@ config LOONGARCH select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select HAVE_POSIX_CPU_TIMERS_TASK_WORK - select HAVE_PREEMPT_DYNAMIC_KEY select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC select HAVE_RETHOOK diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c index 10821cce554c..e8965a3f8082 100644 --- a/arch/loongarch/kernel/paravirt.c +++ b/arch/loongarch/kernel/paravirt.c @@ -308,10 +308,10 @@ int __init pv_time_init(void) static_call_update(pv_steal_clock, paravt_steal_clock); - static_key_slow_inc(¶virt_steal_enabled); + static_branch_inc(¶virt_steal_enabled); #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (steal_acc) - static_key_slow_inc(¶virt_steal_rq_enabled); + static_branch_inc(¶virt_steal_rq_enabled); #endif if (static_key_enabled(&virt_preempt_key)) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 2580e27e4328..143381d267ce 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -279,7 +279,6 @@ config PPC select HAVE_PERF_EVENTS_NMI if PPC64 select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP - select HAVE_PREEMPT_DYNAMIC_KEY select HAVE_POSIX_CPU_TIMERS_TASK_WORK select HAVE_RETHOOK if KPROBES select HAVE_REGS_AND_STACK_ACCESS_API diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c index f29e7547c995..c181df4dec70 100644 --- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c @@ -876,9 +876,9 @@ static void __init pSeries_setup_arch(void) static_branch_enable(&shared_processor); pv_spinlocks_init(); #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING - static_key_slow_inc(¶virt_steal_enabled); + static_branch_inc(¶virt_steal_enabled); if (steal_acc) - static_key_slow_inc(¶virt_steal_rq_enabled); + static_branch_inc(¶virt_steal_rq_enabled); #endif } diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index d6c2dbf8455c..de1923dc6137 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -195,7 +195,6 @@ config RISCV select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select HAVE_POSIX_CPU_TIMERS_TASK_WORK - select HAVE_PREEMPT_DYNAMIC_KEY select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RETHOOK select HAVE_RSEQ diff --git a/arch/riscv/kernel/paravirt.c b/arch/riscv/kernel/paravirt.c index 5f56be79cd06..9c13a6f1ea2a 100644 --- a/arch/riscv/kernel/paravirt.c +++ b/arch/riscv/kernel/paravirt.c @@ -116,9 +116,9 @@ int __init pv_time_init(void) static_call_update(pv_steal_clock, pv_time_steal_clock); - static_key_slow_inc(¶virt_steal_enabled); + static_branch_inc(¶virt_steal_enabled); if (steal_acc) - static_key_slow_inc(¶virt_steal_rq_enabled); + static_branch_inc(¶virt_steal_rq_enabled); pr_info("Computing paravirt steal-time\n"); diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 4b51bc6e8948..2682a2bacc58 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -246,7 +246,6 @@ config S390 select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select HAVE_POSIX_CPU_TIMERS_TASK_WORK - select HAVE_PREEMPT_DYNAMIC_KEY select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RELIABLE_STACKTRACE select HAVE_RETHOOK diff --git a/arch/s390/include/asm/preempt.h b/arch/s390/include/asm/preempt.h index 5560d5fca2a3..60c6f019ec45 100644 --- a/arch/s390/include/asm/preempt.h +++ b/arch/s390/include/asm/preempt.h @@ -155,20 +155,9 @@ static __always_inline int __preempt_count_sub_return(int val) void preempt_schedule(void); void preempt_schedule_notrace(void); -#ifdef CONFIG_PREEMPT_DYNAMIC - -void dynamic_preempt_schedule(void); -void dynamic_preempt_schedule_notrace(void); -#define __preempt_schedule() dynamic_preempt_schedule() -#define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace() - -#else /* CONFIG_PREEMPT_DYNAMIC */ - #define __preempt_schedule() preempt_schedule() #define __preempt_schedule_notrace() preempt_schedule_notrace() -#endif /* CONFIG_PREEMPT_DYNAMIC */ - #endif /* CONFIG_PREEMPTION */ #endif /* __ASM_PREEMPT_H */ diff --git a/arch/s390/kernel/hiperdispatch.c b/arch/s390/kernel/hiperdispatch.c index 217206522266..c21496f0a141 100644 --- a/arch/s390/kernel/hiperdispatch.c +++ b/arch/s390/kernel/hiperdispatch.c @@ -207,16 +207,12 @@ static unsigned long hd_calculate_steal_percentage(void) { unsigned long time_delta, steal_delta, steal, percentage; static ktime_t prev; - int cpus, cpu; + int cpus; ktime_t now; - cpus = 0; - steal = 0; percentage = 0; - for_each_cpu(cpu, &hd_vmvl_cpumask) { - steal += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL]; - cpus++; - } + steal = kcpustat_field_total(CPUTIME_STEAL, &hd_vmvl_cpumask); + cpus = cpumask_weight(&hd_vmvl_cpumask); /* * If there is no vertical medium and low CPUs steal time * is 0 as vertical high CPUs shouldn't experience steal time. diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 15fd9ec5ecac..5a84998b6021 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -297,7 +297,6 @@ config X86 select HAVE_STACK_VALIDATION if HAVE_OBJTOOL select HAVE_STATIC_CALL select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL - select HAVE_PREEMPT_DYNAMIC_CALL select HAVE_RSEQ select HAVE_RUST if X86_64 select HAVE_SYSCALL_TRACEPOINTS diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h index fafb6f8cdac3..d16d9c2f7b08 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -137,43 +137,15 @@ static __always_inline bool should_resched(int preempt_offset) extern asmlinkage void preempt_schedule(void); extern asmlinkage void preempt_schedule_thunk(void); -#define preempt_schedule_dynamic_enabled preempt_schedule_thunk -#define preempt_schedule_dynamic_disabled NULL - extern asmlinkage void preempt_schedule_notrace(void); extern asmlinkage void preempt_schedule_notrace_thunk(void); -#define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace_thunk -#define preempt_schedule_notrace_dynamic_disabled NULL - -#ifdef CONFIG_PREEMPT_DYNAMIC - -DECLARE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled); - -#define __preempt_schedule() \ -do { \ - __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule); \ - asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \ -} while (0) - -DECLARE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled); - -#define __preempt_schedule_notrace() \ -do { \ - __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule_notrace); \ - asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \ -} while (0) - -#else /* PREEMPT_DYNAMIC */ - #define __preempt_schedule() \ asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT); #define __preempt_schedule_notrace() \ asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT); -#endif /* PREEMPT_DYNAMIC */ - #endif /* PREEMPTION */ #undef __pc_op diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c index 34b73573b108..f7ab9e7902cf 100644 --- a/arch/x86/kernel/cpu/vmware.c +++ b/arch/x86/kernel/cpu/vmware.c @@ -328,9 +328,9 @@ static int vmware_cpu_down_prepare(unsigned int cpu) static __init int activate_jump_labels(void) { if (has_steal_clock) { - static_key_slow_inc(¶virt_steal_enabled); + static_branch_inc(¶virt_steal_enabled); if (steal_acc) - static_key_slow_inc(¶virt_steal_rq_enabled); + static_branch_inc(¶virt_steal_rq_enabled); } return 0; diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 6b0a5861ccb8..2ce01fdb8b4b 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -1054,9 +1054,9 @@ const __initconst struct hypervisor_x86 x86_hyper_kvm = { static __init int activate_jump_labels(void) { if (has_steal_clock) { - static_key_slow_inc(¶virt_steal_enabled); + static_branch_inc(¶virt_steal_enabled); if (steal_acc) - static_key_slow_inc(¶virt_steal_rq_enabled); + static_branch_inc(¶virt_steal_rq_enabled); } return 0; diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index 69e52fed4241..747915ff974f 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -391,6 +391,15 @@ static int cpu_uevent(const struct device *dev, struct kobj_uevent_env *env) } #endif +#ifdef CONFIG_PREFERRED_CPU +static ssize_t preferred_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(cpu_preferred_mask)); +} +static DEVICE_ATTR_RO(preferred); +#endif + const struct bus_type cpu_subsys = { .name = "cpu", .dev_name = "cpu", @@ -532,6 +541,9 @@ static struct attribute *cpu_root_attrs[] = { #ifdef CONFIG_GENERIC_CPU_AUTOPROBE &dev_attr_modalias.attr, #endif +#ifdef CONFIG_PREFERRED_CPU + &dev_attr_preferred.attr, +#endif NULL }; diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig index 52eb7e4ba71f..eeb84e578ddf 100644 --- a/drivers/virt/Kconfig +++ b/drivers/virt/Kconfig @@ -41,6 +41,23 @@ config FSL_HV_MANAGER 4) A kernel interface for receiving callbacks when a managed partition shuts down. +config STEAL_GOVERNOR + tristate "Dynamic vCPU management based on steal time" + depends on PARAVIRT && SMP + select PREFERRED_CPU + default m + help + This driver helps to reduce the steal time in paravirtualized + environments, thereby reducing vCPU preemption costs. + + By default preferred CPUs will be same as active CPUs. Depending + on the steal time when steal_governor driver is enabled, + preferred CPUs could become subset of active CPUs. + More details are at: Documentation/driver-api/steal-governor.rst + + It is recommended to build it as module and load the module + to enable it. + source "drivers/virt/vboxguest/Kconfig" source "drivers/virt/nitro_enclaves/Kconfig" diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile index f29901bd7820..05fb075ef5b8 100644 --- a/drivers/virt/Makefile +++ b/drivers/virt/Makefile @@ -5,6 +5,7 @@ obj-$(CONFIG_FSL_HV_MANAGER) += fsl_hypervisor.o obj-$(CONFIG_VMGENID) += vmgenid.o +obj-$(CONFIG_STEAL_GOVERNOR) += steal_governor.o obj-y += vboxguest/ obj-$(CONFIG_NITRO_ENCLAVES) += nitro_enclaves/ diff --git a/drivers/virt/steal_governor.c b/drivers/virt/steal_governor.c new file mode 100644 index 000000000000..6e31f9923dea --- /dev/null +++ b/drivers/virt/steal_governor.c @@ -0,0 +1,296 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Steal time governor driver periodically computes steal time. + * Based on the thresholds it either reduce/increase the preferred + * CPUs which can be used by the workload to avoid vCPU preemption + * to an extent possible in paravirtualized environment. + * + * Available with CONFIG_STEAL_GOVERNOR + * + * Copyright (C) 2026 IBM + * Author: Shrikanth Hegde <sshegde@linux.ibm.com> + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/cleanup.h> +#include <linux/cpuhplock.h> +#include <linux/cpumask.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/kernel_stat.h> +#include <linux/kconfig.h> +#include <linux/ktime.h> +#include <linux/math64.h> +#include <linux/module.h> +#include <linux/sched/isolation.h> +#include <linux/topology.h> +#include <linux/types.h> +#include <linux/workqueue.h> +#ifdef CONFIG_XEN +#include <xen/xen.h> +#endif + +#if !IS_ENABLED(CONFIG_PREFERRED_CPU) +#error "Steal Governor requires CONFIG_PREFERRED_CPU" +#endif + +struct steal_governor { + ktime_t time; + u64 steal; + unsigned long delay; + unsigned int interval_ms; + unsigned int high_threshold; + unsigned int low_threshold; + struct delayed_work work; +}; + +static struct steal_governor sg_ctx = { + .interval_ms = 1000, /* 1 second */ + .high_threshold = 500, /* 5% */ + .low_threshold = 200, /* 2% */ +}; + +static void restore_preferred_to_active(void) +{ + int cpu; + + guard(cpus_read_lock)(); + for_each_cpu(cpu, cpu_active_mask) + set_cpu_preferred(cpu, true); +} + +static int param_set_interval_ms(const char *val, const struct kernel_param *kp) +{ + unsigned int interval; + int ret; + + ret = kstrtouint(val, 0, &interval); + if (ret) + return ret; + + if (interval < 100 || interval > 100000) { + pr_err("interval_ms must be between 100 and 100000\n"); + return -EINVAL; + } + + return param_set_uint(val, kp); +} + +static const struct kernel_param_ops interval_ms_ops = { + .set = param_set_interval_ms, + .get = param_get_uint, +}; + +module_param_cb(interval_ms, &interval_ms_ops, &sg_ctx.interval_ms, 0444); +MODULE_PARM_DESC(interval_ms, + "Sampling frequency in milliseconds. default: 1000"); + +static int param_set_high_threshold(const char *val, const struct kernel_param *kp) +{ + unsigned int threshold; + int ret; + + ret = kstrtouint(val, 0, &threshold); + if (ret) + return ret; + + if (threshold >= 100 * 100) { + pr_err("high_threshold (%u) can't be more than 99.99%%\n", threshold); + return -EINVAL; + } + + return param_set_uint(val, kp); +} + +static const struct kernel_param_ops high_threshold_ops = { + .set = param_set_high_threshold, + .get = param_get_uint, +}; + +module_param_cb(high_threshold, &high_threshold_ops, &sg_ctx.high_threshold, 0444); +MODULE_PARM_DESC(high_threshold, + "High steal threshold. default: 500 i.e 5%. Must be > low_threshold"); + +module_param_named(low_threshold, sg_ctx.low_threshold, uint, 0444); +MODULE_PARM_DESC(low_threshold, + "Low steal threshold. default: 200 i.e 2%. Must be < high_threshold"); + +/* Return collective steal time across system. */ +static u64 get_system_steal_time(void) +{ + return kcpustat_field_total(CPUTIME_STEAL, cpu_possible_mask); +} + +/* Return number of CPUs to consider for steal ratio. */ +static unsigned int get_system_cpus(void) +{ + return num_active_cpus(); +} + +/* + * Called when the steal governor detects high physical CPU contention. + * It finds the last active core in the preferred mask and mark those + * CPUs as non-preferred. + * + * Must ensure: + * - at least one core is always kept as preferred + * - preferred is always subset of active. + */ +static void decrease_preferred_cpus(void) +{ + const struct cpumask *first_hk_core; + int target_cpu = nr_cpu_ids; + int cpu; + + guard(cpus_read_lock)(); + cpu = cpumask_first_and(housekeeping_cpumask(HK_TYPE_KERNEL_NOISE), + cpu_preferred_mask); + if (cpu >= nr_cpu_ids) + return; + + /* Always leave first housekeeping core as preferred. */ + first_hk_core = topology_sibling_cpumask(cpu); + cpu = cpumask_last(cpu_preferred_mask); + if (cpu >= nr_cpu_ids) + return; + + /* Find the last CPU which doesn't belong to that first hk_core. */ + if (!cpumask_test_cpu(cpu, first_hk_core)) { + target_cpu = cpu; + } else { + for_each_cpu_andnot(cpu, cpu_preferred_mask, first_hk_core) + target_cpu = cpu; + } + + /* Only the first housekeeping core remains */ + if (target_cpu >= nr_cpu_ids) + return; + + for_each_cpu_and(cpu, topology_sibling_cpumask(target_cpu), + cpu_preferred_mask) + set_cpu_preferred(cpu, false); +} + +/* + * Called when the steal governor detects no/low physical CPU contention. + * It finds the first active core outside of preferred mask and mark + * those CPUs as preferred. + * + * Must ensure preferred is subset of active. + */ +static void increase_preferred_cpus(void) +{ + int first_cpu, cpu; + + guard(cpus_read_lock)(); + first_cpu = cpumask_first_andnot(cpu_active_mask, cpu_preferred_mask); + + /* All CPUs are preferred. Nothing to increase further */ + if (first_cpu >= nr_cpu_ids) + return; + + for_each_cpu_and(cpu, topology_sibling_cpumask(first_cpu), + cpu_active_mask) + set_cpu_preferred(cpu, true); +} + +static bool preferred_cpus_valid(void) +{ + if (cpumask_empty(cpu_preferred_mask)) { + pr_err("empty preferred mask. stopping\n"); + return false; + } + + if (!cpumask_subset(cpu_preferred_mask, cpu_active_mask)) { + pr_err("preferred: %*pbl is not subset of active: %*pbl, stopping\n", + cpumask_pr_args(cpu_preferred_mask), + cpumask_pr_args(cpu_active_mask)); + return false; + } + + return true; +} + +static void steal_governor_loop(struct work_struct *work) +{ + u64 curr_steal, delta_steal, delta_ns, steal_ratio; + ktime_t now; + + now = ktime_get(); + delta_ns = ktime_to_ns(ktime_sub(now, sg_ctx.time)); + + if (unlikely(delta_ns < NSEC_PER_MSEC)) { + pr_err_ratelimited("work scheduled too soon delta_ns: %llu\n", delta_ns); + goto requeue_work; + } + + curr_steal = get_system_steal_time(); + delta_steal = curr_steal > sg_ctx.steal ? curr_steal - sg_ctx.steal : 0; + sg_ctx.steal = curr_steal; + sg_ctx.time = now; + + /* + * steal_ratio = (delta_steal * 100*100)/(delta_ns * num_cpus()) + * To avoid possible overflow, divide the denominator early. + * Note minimum interval is 100ms. + */ + delta_ns = max_t(u64, div_u64(delta_ns * get_system_cpus(), 10000), 1); + steal_ratio = div64_u64(delta_steal, delta_ns); + + if (steal_ratio > sg_ctx.high_threshold) + decrease_preferred_cpus(); + else if (steal_ratio <= sg_ctx.low_threshold) + increase_preferred_cpus(); + /* + * else: steal ratio is within bounds. Still do design checks so that + * module restores to active if CPU hotplug breaks those assumptions. + */ + if (!preferred_cpus_valid()) { + restore_preferred_to_active(); + return; + } + +requeue_work: + schedule_delayed_work(&sg_ctx.work, sg_ctx.delay); +} + +static int __init steal_governor_init(void) +{ +#ifdef CONFIG_XEN + if (xen_initial_domain()) { + pr_err("Cannot load in Xen Dom0 (Host OS). Driver is for guests only.\n"); + return -ENODEV; + } +#endif + + if (sg_ctx.low_threshold >= sg_ctx.high_threshold) { + pr_err("low_threshold (%u) must be less than high_threshold (%u)\n", + sg_ctx.low_threshold, sg_ctx.high_threshold); + return -EINVAL; + } + + sg_ctx.delay = msecs_to_jiffies(sg_ctx.interval_ms); + INIT_DELAYED_WORK(&sg_ctx.work, steal_governor_loop); + sg_ctx.steal = get_system_steal_time(); + sg_ctx.time = ktime_get(); + schedule_delayed_work(&sg_ctx.work, sg_ctx.delay); + pr_info("enabled. interval: %ums, high_threshold: %u, low_threshold: %u\n", + sg_ctx.interval_ms, sg_ctx.high_threshold, sg_ctx.low_threshold); + + return 0; +} + +static void __exit steal_governor_exit(void) +{ + disable_delayed_work_sync(&sg_ctx.work); + restore_preferred_to_active(); + pr_info("disabled\n"); +} + +module_init(steal_governor_init); +module_exit(steal_governor_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("IBM Corporation"); +MODULE_DESCRIPTION("Virtualization Steal Time Governor"); diff --git a/drivers/xen/time.c b/drivers/xen/time.c index a2be0a4d45b0..a02d48a2aa68 100644 --- a/drivers/xen/time.c +++ b/drivers/xen/time.c @@ -169,7 +169,7 @@ void __init xen_time_setup_guest(void) static_call_update(pv_steal_clock, xen_steal_clock); - static_key_slow_inc(¶virt_steal_enabled); + static_branch_inc(¶virt_steal_enabled); if (xen_runstate_remote) - static_key_slow_inc(¶virt_steal_rq_enabled); + static_branch_inc(¶virt_steal_rq_enabled); } diff --git a/fs/proc/uptime.c b/fs/proc/uptime.c index 433aa947cd57..53143c66cbe1 100644 --- a/fs/proc/uptime.c +++ b/fs/proc/uptime.c @@ -15,12 +15,8 @@ static int uptime_proc_show(struct seq_file *m, void *v) struct timespec64 idle; u64 idle_nsec; u32 rem; - int i; - - idle_nsec = 0; - for_each_possible_cpu(i) - idle_nsec += kcpustat_field(CPUTIME_IDLE, i); + idle_nsec = kcpustat_field_total(CPUTIME_IDLE, cpu_possible_mask); ktime_get_boottime_ts64(&uptime); timens_add_boottime(&uptime); diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h index c8683c046615..1adddeab8545 100644 --- a/include/asm-generic/preempt.h +++ b/include/asm-generic/preempt.h @@ -96,19 +96,9 @@ static __always_inline bool should_resched(int preempt_offset) extern asmlinkage void preempt_schedule(void); extern asmlinkage void preempt_schedule_notrace(void); -#if defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) - -void dynamic_preempt_schedule(void); -void dynamic_preempt_schedule_notrace(void); -#define __preempt_schedule() dynamic_preempt_schedule() -#define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace() - -#else /* !CONFIG_PREEMPT_DYNAMIC || !CONFIG_HAVE_PREEMPT_DYNAMIC_KEY*/ - #define __preempt_schedule() preempt_schedule() #define __preempt_schedule_notrace() preempt_schedule_notrace() -#endif /* CONFIG_PREEMPT_DYNAMIC && CONFIG_HAVE_PREEMPT_DYNAMIC_KEY*/ #endif /* CONFIG_PREEMPTION */ #endif /* __ASM_PREEMPT_H */ diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 7df1573a409c..adafbcf2016b 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -52,6 +52,7 @@ struct device; * bitmap_complement(dst, src, nbits) *dst = ~(*src) * bitmap_equal(src1, src2, nbits) Are *src1 and *src2 equal? * bitmap_intersects(src1, src2, nbits) Do *src1 and *src2 overlap? + * bitmap_intersects_and(src1, src2, src3, nbits) Do *src1, *src2 and *src3 overlap? * bitmap_subset(src1, src2, nbits) Is *src1 a subset of *src2? * bitmap_empty(src, nbits) Are all bits zero in *src? * bitmap_full(src, nbits) Are all bits set in *src? @@ -181,6 +182,9 @@ void __bitmap_replace(unsigned long *dst, const unsigned long *mask, unsigned int nbits); bool __bitmap_intersects(const unsigned long *bitmap1, const unsigned long *bitmap2, unsigned int nbits); +bool __bitmap_intersects_and(const unsigned long *bitmap1, + const unsigned long *bitmap2, + const unsigned long *bitmap3, unsigned int nbits); bool __bitmap_subset(const unsigned long *bitmap1, const unsigned long *bitmap2, unsigned int nbits); unsigned int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits); @@ -446,6 +450,16 @@ bool bitmap_intersects(const unsigned long *src1, const unsigned long *src2, uns } static __always_inline +bool bitmap_intersects_and(const unsigned long *src1, const unsigned long *src2, + const unsigned long *src3, unsigned int nbits) +{ + if (small_const_nbits(nbits)) + return ((*src1 & *src2 & *src3) & BITMAP_LAST_WORD_MASK(nbits)) != 0; + else + return __bitmap_intersects_and(src1, src2, src3, nbits); +} + +static __always_inline bool bitmap_subset(const unsigned long *src1, const unsigned long *src2, unsigned int nbits) { if (small_const_nbits(nbits)) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 4c8bb6953107..bf89bb3f30f6 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -121,12 +121,20 @@ extern struct cpumask __cpu_enabled_mask; extern struct cpumask __cpu_present_mask; extern struct cpumask __cpu_active_mask; extern struct cpumask __cpu_dying_mask; + +#ifdef CONFIG_PREFERRED_CPU +extern struct cpumask __cpu_preferred_mask; +#else +#define __cpu_preferred_mask __cpu_active_mask +#endif + #define cpu_possible_mask ((const struct cpumask *)&__cpu_possible_mask) #define cpu_online_mask ((const struct cpumask *)&__cpu_online_mask) #define cpu_enabled_mask ((const struct cpumask *)&__cpu_enabled_mask) #define cpu_present_mask ((const struct cpumask *)&__cpu_present_mask) #define cpu_active_mask ((const struct cpumask *)&__cpu_active_mask) #define cpu_dying_mask ((const struct cpumask *)&__cpu_dying_mask) +#define cpu_preferred_mask ((const struct cpumask *)&__cpu_preferred_mask) extern atomic_t __num_online_cpus; extern unsigned int __num_possible_cpus; @@ -825,6 +833,24 @@ bool cpumask_intersects(const struct cpumask *src1p, const struct cpumask *src2p } /** + * cpumask_intersects_and - (*src1p & *src2p & *src3p) != 0 + * @src1p: the first input + * @src2p: the second input + * @src3p: the third input + * + * Return: true if AND of the three cpumasks is non-empty, + * otherwise false + */ +static __always_inline +bool cpumask_intersects_and(const struct cpumask *src1p, + const struct cpumask *src2p, + const struct cpumask *src3p) +{ + return bitmap_intersects_and(cpumask_bits(src1p), cpumask_bits(src2p), + cpumask_bits(src3p), small_cpumask_bits); +} + +/** * cpumask_subset - (*src1p & ~*src2p) == 0 * @src1p: the first input * @src2p: the second input @@ -1163,6 +1189,12 @@ void init_cpu_possible(const struct cpumask *src); #define set_cpu_active(cpu, active) assign_cpu((cpu), &__cpu_active_mask, (active)) #define set_cpu_dying(cpu, dying) assign_cpu((cpu), &__cpu_dying_mask, (dying)) +#ifdef CONFIG_PREFERRED_CPU +#define set_cpu_preferred(cpu, preferred) assign_cpu((cpu), &__cpu_preferred_mask, (preferred)) +#else +#define set_cpu_preferred(cpu, preferred) do { } while (0) +#endif + void set_cpu_online(unsigned int cpu, bool online); void set_cpu_possible(unsigned int cpu, bool possible); @@ -1257,6 +1289,11 @@ static __always_inline bool cpu_dying(unsigned int cpu) return cpumask_test_cpu(cpu, cpu_dying_mask); } +static __always_inline bool cpu_preferred(unsigned int cpu) +{ + return cpumask_test_cpu(cpu, cpu_preferred_mask); +} + #else #define num_online_cpus() 1U @@ -1295,6 +1332,11 @@ static __always_inline bool cpu_dying(unsigned int cpu) return false; } +static __always_inline bool cpu_preferred(unsigned int cpu) +{ + return cpu == 0; +} + #endif /* NR_CPUS > 1 */ #define cpu_is_offline(cpu) unlikely(!cpu_online(cpu)) diff --git a/include/linux/irq-entry-common.h b/include/linux/irq-entry-common.h index 0bb6c03481fa..2be273bb68f0 100644 --- a/include/linux/irq-entry-common.h +++ b/include/linux/irq-entry-common.h @@ -346,22 +346,7 @@ typedef struct irqentry_state { * * Conditional reschedule with additional sanity checks. */ -void raw_irqentry_exit_cond_resched(void); - -#ifdef CONFIG_PREEMPT_DYNAMIC -#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) -#define irqentry_exit_cond_resched_dynamic_enabled raw_irqentry_exit_cond_resched -#define irqentry_exit_cond_resched_dynamic_disabled NULL -DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched); -#define irqentry_exit_cond_resched() static_call(irqentry_exit_cond_resched)() -#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) -DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); -void dynamic_irqentry_exit_cond_resched(void); -#define irqentry_exit_cond_resched() dynamic_irqentry_exit_cond_resched() -#endif -#else /* CONFIG_PREEMPT_DYNAMIC */ -#define irqentry_exit_cond_resched() raw_irqentry_exit_cond_resched() -#endif /* CONFIG_PREEMPT_DYNAMIC */ +void irqentry_exit_cond_resched(void); /** * irqentry_enter_from_kernel_mode - Establish state before invoking the irq handler diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h index c5afd053ae32..7184e1273965 100644 --- a/include/linux/irq_work.h +++ b/include/linux/irq_work.h @@ -59,6 +59,7 @@ void irq_work_sync(struct irq_work *work); #include <asm/irq_work.h> void irq_work_run(void); +void irq_work_run_cpu(unsigned int cpu); bool irq_work_needs_cpu(void); void irq_work_single(void *arg); @@ -67,6 +68,7 @@ void arch_irq_work_raise(void); #else static inline bool irq_work_needs_cpu(void) { return false; } static inline void irq_work_run(void) { } +static inline void irq_work_run_cpu(unsigned int cpu) { } static inline void irq_work_single(void *arg) { } #endif diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 24414c79e59a..4b11d1dc0a67 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -43,30 +43,10 @@ struct completion; struct user; #ifdef CONFIG_PREEMPT_VOLUNTARY_BUILD - extern int __cond_resched(void); # define might_resched() __cond_resched() - -#elif defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) - -extern int __cond_resched(void); - -DECLARE_STATIC_CALL(might_resched, __cond_resched); - -static __always_inline void might_resched(void) -{ - static_call_mod(might_resched)(); -} - -#elif defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) - -extern int dynamic_might_resched(void); -# define might_resched() dynamic_might_resched() - #else - # define might_resched() do { } while (0) - #endif /* CONFIG_PREEMPT_* */ #ifdef CONFIG_DEBUG_ATOMIC_SLEEP diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h index 9ca6c2259dfe..c1e85550bf12 100644 --- a/include/linux/kernel_stat.h +++ b/include/linux/kernel_stat.h @@ -196,6 +196,17 @@ static inline void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu) } #endif /* !CONFIG_VIRT_CPU_ACCOUNTING_GEN */ +static inline u64 kcpustat_field_total(enum cpu_usage_stat usage, const struct cpumask *cpus) +{ + u64 total = 0; + int cpu; + + for_each_cpu(cpu, cpus) + total += kcpustat_field(usage, cpu); + + return total; +} + extern void account_user_time(struct task_struct *, u64); extern void account_guest_time(struct task_struct *, u64); extern void account_system_time(struct task_struct *, int, u64); diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 2e689de7b29a..06ff44a4b8b6 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -498,21 +498,11 @@ DEFINE_LOCK_GUARD_0(preempt_notrace, preempt_disable_notrace(), preempt_enable_n #ifdef CONFIG_PREEMPT_DYNAMIC -extern bool preempt_model_none(void); -extern bool preempt_model_voluntary(void); extern bool preempt_model_full(void); extern bool preempt_model_lazy(void); #else -static inline bool preempt_model_none(void) -{ - return IS_ENABLED(CONFIG_PREEMPT_NONE); -} -static inline bool preempt_model_voluntary(void) -{ - return IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY); -} static inline bool preempt_model_full(void) { return IS_ENABLED(CONFIG_PREEMPT); @@ -525,6 +515,16 @@ static inline bool preempt_model_lazy(void) #endif +static inline bool preempt_model_none(void) +{ + return IS_ENABLED(CONFIG_PREEMPT_NONE); +} + +static inline bool preempt_model_voluntary(void) +{ + return IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY); +} + static inline bool preempt_model_rt(void) { return IS_ENABLED(CONFIG_PREEMPT_RT); diff --git a/include/linux/sched.h b/include/linux/sched.h index d35ae49a991f..0cb03f9acfe3 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -554,6 +554,7 @@ struct sched_statistics { u64 nr_failed_migrations_running; u64 nr_failed_migrations_hot; u64 nr_forced_migrations; + u64 nr_migrations_cpu_non_preferred; u64 nr_wakeups; u64 nr_wakeups_sync; @@ -2105,10 +2106,9 @@ static inline int test_tsk_thread_flag(struct task_struct *tsk, int flag) static inline void set_tsk_need_resched(struct task_struct *tsk) { - if (tracepoint_enabled(sched_set_need_resched_tp) && - !test_tsk_thread_flag(tsk, TIF_NEED_RESCHED)) + if (!test_and_set_tsk_thread_flag(tsk, TIF_NEED_RESCHED) && + tracepoint_enabled(sched_set_need_resched_tp)) __trace_set_need_resched(tsk, TIF_NEED_RESCHED); - set_tsk_thread_flag(tsk,TIF_NEED_RESCHED); } static inline void clear_tsk_need_resched(struct task_struct *tsk) @@ -2135,44 +2135,19 @@ static inline void set_need_resched_current(void) * value indicates whether a reschedule was done in fact. * cond_resched_lock() will drop the spinlock before scheduling, */ -#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) +#if !defined(CONFIG_PREEMPTION) extern int __cond_resched(void); -#if defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) - -DECLARE_STATIC_CALL(cond_resched, __cond_resched); - -static __always_inline int _cond_resched(void) -{ - return static_call_mod(cond_resched)(); -} - -#elif defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) - -extern int dynamic_cond_resched(void); - -static __always_inline int _cond_resched(void) -{ - return dynamic_cond_resched(); -} - -#else /* !CONFIG_PREEMPTION */ - static inline int _cond_resched(void) { return __cond_resched(); } - -#endif /* PREEMPT_DYNAMIC && CONFIG_HAVE_PREEMPT_DYNAMIC_CALL */ - -#else /* CONFIG_PREEMPTION && !CONFIG_PREEMPT_DYNAMIC */ - +#else static inline int _cond_resched(void) { return 0; } - -#endif /* !CONFIG_PREEMPTION || CONFIG_PREEMPT_DYNAMIC */ +#endif #define cond_resched() ({ \ __might_resched(__FILE__, __LINE__, 0); \ diff --git a/include/linux/sched/cputime.h b/include/linux/sched/cputime.h index e90efaf6d26e..694126411dfe 100644 --- a/include/linux/sched/cputime.h +++ b/include/linux/sched/cputime.h @@ -182,9 +182,9 @@ extern unsigned long long task_sched_runtime(struct task_struct *task); #ifdef CONFIG_PARAVIRT -struct static_key; -extern struct static_key paravirt_steal_enabled; -extern struct static_key paravirt_steal_rq_enabled; +#include <linux/jump_label.h> +DECLARE_STATIC_KEY_FALSE(paravirt_steal_enabled); +DECLARE_STATIC_KEY_FALSE(paravirt_steal_rq_enabled); #ifdef CONFIG_HAVE_PV_STEAL_CLOCK_GEN u64 dummy_steal_clock(int cpu); diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 33a4624285cd..19ffeba89428 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -53,7 +53,7 @@ */ #define UNSHARE_EMPTY_MNTNS 0x00100000 /* Unshare an empty mount namespace. */ -#ifndef __ASSEMBLY__ +#ifndef __ASSEMBLER__ /** * struct clone_args - arguments for the clone3 syscall * @flags: Flags for the new process as listed above. diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index f294dad43bd7..edc067a0c422 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -132,10 +132,9 @@ config PREEMPTION config PREEMPT_DYNAMIC bool "Preemption behaviour defined on boot" - depends on HAVE_PREEMPT_DYNAMIC - select JUMP_LABEL if HAVE_PREEMPT_DYNAMIC_KEY + depends on ARCH_HAS_PREEMPT_LAZY select PREEMPT_BUILD - default y if HAVE_PREEMPT_DYNAMIC_CALL + default y help This option allows to define the preemption model on the kernel command line parameter and thus override the default preemption @@ -145,9 +144,7 @@ config PREEMPT_DYNAMIC provide a pre-built kernel binary to reduce the number of kernel flavors they offer while still offering different usecases. - The runtime overhead is negligible with HAVE_STATIC_CALL_INLINE enabled - but if runtime patching is not available for the specific architecture - then the potential overhead should be considered. + The runtime overhead is negligible. Interesting if you want the same pre-built kernel should be used for both Server and Desktop workloads. @@ -197,3 +194,7 @@ config SCHED_CLASS_EXT For more information: Documentation/scheduler/sched-ext.rst https://github.com/sched-ext/scx + +config PREFERRED_CPU + bool + depends on SMP && PARAVIRT diff --git a/kernel/cpu.c b/kernel/cpu.c index b3c8553d7bd6..376d297a6292 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -3103,6 +3103,11 @@ EXPORT_SYMBOL(__cpu_dying_mask); atomic_t __num_online_cpus __read_mostly; EXPORT_SYMBOL(__num_online_cpus); +#ifdef CONFIG_PREFERRED_CPU +struct cpumask __cpu_preferred_mask __read_mostly; +EXPORT_SYMBOL_GPL(__cpu_preferred_mask); +#endif + void init_cpu_present(const struct cpumask *src) { cpumask_copy(&__cpu_present_mask, src); @@ -3160,6 +3165,7 @@ void __init boot_cpu_init(void) /* Mark the boot cpu "present", "online" etc for SMP and UP case */ set_cpu_online(cpu, true); set_cpu_active(cpu, true); + set_cpu_preferred(cpu, true); set_cpu_present(cpu, true); set_cpu_possible(cpu, true); diff --git a/kernel/entry/common.c b/kernel/entry/common.c index e3d381fd3d25..e234b04373fe 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -123,7 +123,7 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs) /** * arch_irqentry_exit_need_resched - Architecture specific need resched function * - * Invoked from raw_irqentry_exit_cond_resched() to check if resched is needed. + * Invoked from irqentry_exit_cond_resched() to check if resched is needed. * Defaults return true. * * The main purpose is to permit arch to avoid preemption of a task from an IRQ. @@ -134,7 +134,7 @@ static inline bool arch_irqentry_exit_need_resched(void); static inline bool arch_irqentry_exit_need_resched(void) { return true; } #endif -void raw_irqentry_exit_cond_resched(void) +void irqentry_exit_cond_resched(void) { if (!preempt_count()) { /* Sanity check RCU and thread stack */ @@ -145,19 +145,6 @@ void raw_irqentry_exit_cond_resched(void) preempt_schedule_irq(); } } -#ifdef CONFIG_PREEMPT_DYNAMIC -#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) -DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched); -#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) -DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); -void dynamic_irqentry_exit_cond_resched(void) -{ - if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched)) - return; - raw_irqentry_exit_cond_resched(); -} -#endif -#endif noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state) { diff --git a/kernel/irq_work.c b/kernel/irq_work.c index f7e2dc2c30c6..73eabcbdcd50 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -252,10 +252,7 @@ static void irq_work_run_list(struct llist_head *list) irq_work_single(work); } -/* - * hotplug calls this through: - * hotplug_cfd() -> flush_smp_call_function_queue() - */ +/* CPU hotplug calls this through smpcfd_dying_cpu() */ void irq_work_run(void) { irq_work_run_list(this_cpu_ptr(&raised_list)); @@ -266,6 +263,17 @@ void irq_work_run(void) } EXPORT_SYMBOL_GPL(irq_work_run); +void irq_work_run_cpu(unsigned int cpu) +{ + if (WARN_ON_ONCE(!cpumask_test_cpu(cpu, cpu_dying_mask))) + return; + + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + return; + + irq_work_run_list(per_cpu_ptr(&lazy_list, cpu)); +} + void irq_work_tick(void) { struct llist_head *raised = this_cpu_ptr(&raised_list); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 1fe40de6ebe3..047fbe8ef298 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -805,7 +805,7 @@ struct rq *_task_rq_lock(struct task_struct *p, struct rq_flags *rf) /* Use CONFIG_PARAVIRT as this will avoid more #ifdef in arch code. */ #ifdef CONFIG_PARAVIRT -struct static_key paravirt_steal_rq_enabled; +DEFINE_STATIC_KEY_FALSE(paravirt_steal_rq_enabled); #endif static void update_rq_clock_task(struct rq *rq, s64 delta) @@ -844,7 +844,7 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) } #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING - if (static_key_false((¶virt_steal_rq_enabled))) { + if (static_branch_unlikely(¶virt_steal_rq_enabled)) { u64 prev_steal; steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); @@ -1196,6 +1196,7 @@ static void __resched_curr(struct rq *rq, int tif) { struct task_struct *curr = rq->curr; struct thread_info *cti = task_thread_info(curr); + bool need_ipi; int cpu; lockdep_assert_rq_held(rq); @@ -1212,15 +1213,17 @@ static void __resched_curr(struct rq *rq, int tif) cpu = cpu_of(rq); - trace_sched_set_need_resched_tp(curr, cpu, tif); if (cpu == smp_processor_id()) { set_ti_thread_flag(cti, tif); if (tif == TIF_NEED_RESCHED) set_preempt_need_resched(); + trace_sched_set_need_resched_tp(curr, cpu, tif); return; } - if (set_nr_and_not_polling(cti, tif)) { + need_ipi = set_nr_and_not_polling(cti, tif); + trace_sched_set_need_resched_tp(curr, cpu, tif); + if (need_ipi) { if (tif == TIF_NEED_RESCHED) smp_send_reschedule(cpu); } else { @@ -2252,7 +2255,8 @@ void deactivate_task(struct rq *rq, struct task_struct *p, int flags) dequeue_task(rq, p, flags); } -static void block_task(struct rq *rq, struct task_struct *p, unsigned long task_state) +static bool dequeue_block_task(struct rq *rq, struct task_struct *p, + unsigned long task_state) { int flags = DEQUEUE_NOCLOCK; @@ -2273,9 +2277,15 @@ static void block_task(struct rq *rq, struct task_struct *p, unsigned long task_ * * Where __schedule() and ttwu() have matching control dependencies. * - * After this, schedule() must not care about p->state any more. + * Once the caller invokes __block_task(), schedule() must not care about + * p->state any more. */ - if (dequeue_task(rq, p, DEQUEUE_SLEEP | flags)) + return dequeue_task(rq, p, DEQUEUE_SLEEP | flags); +} + +static void block_task(struct rq *rq, struct task_struct *p, unsigned long task_state) +{ + if (dequeue_block_task(rq, p, task_state)) __block_task(rq, p); } @@ -2504,6 +2514,24 @@ static inline bool rq_has_pinned_tasks(struct rq *rq) return rq->nr_pinned; } +static inline bool task_can_migrate_to_preferred(struct task_struct *p, int cpu) +{ + /* No need to migrate from a preferred CPU */ + if (cpu_preferred(cpu)) + return false; + + /* Only FAIR tasks honor preferred CPU state */ + if (unlikely(p->sched_class != &fair_sched_class)) + return false; + + /* Ignore preferred state if task affinity is changing */ + if (unlikely(!cpumask_test_cpu(task_cpu(p), p->cpus_ptr))) + return false; + + return cpumask_intersects_and(p->cpus_ptr, cpu_preferred_mask, + task_cpu_possible_mask(p)); +} + /* * Per-CPU kthreads are allowed to run on !active && online CPUs, see * __set_cpus_allowed_ptr() and select_fallback_rq(). @@ -2519,8 +2547,12 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) return cpu_online(cpu); /* Non kernel threads are not allowed during either online or offline. */ - if (!(p->flags & PF_KTHREAD)) + if (!(p->flags & PF_KTHREAD)) { + /* Try to use preferred CPU if task's affinity allows */ + if (task_can_migrate_to_preferred(p, cpu)) + return false; return cpu_active(cpu); + } /* KTHREAD_IS_PER_CPU is always allowed. */ if (kthread_is_per_cpu(p)) @@ -2530,7 +2562,11 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) if (cpu_dying(cpu)) return false; - /* But are allowed during online. */ + /* Try to keep unbound kthreads on a preferred CPU if possible. */ + if (task_can_migrate_to_preferred(p, cpu)) + return false; + + /* Otherwise, they are allowed to run on online CPU. */ return cpu_online(cpu); } @@ -3773,6 +3809,7 @@ static inline void proxy_reset_donor(struct rq *rq) WARN_ON_ONCE(rq->donor == rq->curr); put_prev_set_next_task(rq, rq->donor, rq->curr); + rq->next_class = rq->curr->sched_class; rq_set_donor(rq, rq->curr); zap_balance_callbacks(rq); resched_curr(rq); @@ -3787,6 +3824,8 @@ static inline void proxy_reset_donor(struct rq *rq) */ static inline bool proxy_needs_return(struct rq *rq, struct task_struct *p) { + bool dequeued; + /* * Typically per __set_task_cpu(), task_cpu(p) == p->wake_cpu. * @@ -3809,12 +3848,23 @@ static inline bool proxy_needs_return(struct rq *rq, struct task_struct *p) /* If already current, don't need to return migrate */ if (task_current(rq, p)) return false; - - /* If we're return migrating the rq->donor, switch it out for idle */ - if (task_current_donor(rq, p)) - proxy_reset_donor(rq); } - block_task(rq, p, TASK_WAKING); + + dequeued = dequeue_block_task(rq, p, TASK_WAKING); + + /* + * Dequeue @p from its scheduling class before resetting rq->donor. + * In particular, sched_ext needs to end the donor's running session + * and clear SCX_TASK_QUEUED before put_prev_task_scx() is called by + * proxy_reset_donor(); otherwise it would reenqueue the blocked donor. + * + * Keep on_rq set until all donor references have been replaced. + */ + if (task_current_donor(rq, p)) + proxy_reset_donor(rq); + + if (dequeued) + __block_task(rq, p); return true; } #else /* !CONFIG_SCHED_PROXY_EXEC */ @@ -3905,7 +3955,7 @@ static int ttwu_runnable(struct task_struct *p, int wake_flags) * When on_rq && !on_cpu the task is preempted, see if * it should preempt the task that is current now. */ - wakeup_preempt(rq, p, wake_flags); + wakeup_preempt(rq, p, wake_flags | WF_TTWU_RQ); } ttwu_do_wakeup(p); return 1; @@ -5149,7 +5199,7 @@ static void do_balance_callbacks(struct rq *rq, struct balance_callback *head) lockdep_assert_rq_held(rq); while (head) { - func = (void (*)(struct rq *))head->func; + func = head->func; next = head->next; head->next = NULL; head = next; @@ -5789,6 +5839,9 @@ void sched_tick(void) unsigned long hw_pressure; u64 resched_latency; + if (!cpu_preferred(cpu)) + sched_push_current_non_preferred_cpu(rq); + if (housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE)) arch_scale_freq_tick(); @@ -6283,10 +6336,7 @@ pick_next_task(struct rq *rq, struct rq_flags *rf) * selection. In this case, do a core-wide selection. */ if (rq->core->core_pick_seq == rq->core->core_task_seq && - rq->core->core_pick_seq != rq->core_sched_seq && rq->core_pick) { - WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq); - next = rq->core_pick; rq->dl_server = rq->core_dl_server; rq->core_pick = NULL; @@ -6318,11 +6368,13 @@ restart: } /* - * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq + * core->core_task_seq, core->core_pick_seq * * @task_seq guards the task state ({en,de}queues) * @pick_seq is the @task_seq we did a selection on - * @sched_seq is the @pick_seq we scheduled + * + * Once a core-wide selection is committed, a non-NULL core_pick denotes + * a pick which still needs to be consumed on this CPU. * * However, preemptions can cause multiple picks on the same task set. * 'Fix' this by also increasing @task_seq for every pick. @@ -6429,7 +6481,6 @@ restart: rq->core->core_pick_seq = rq->core->core_task_seq; next = rq->core_pick; - rq->core_sched_seq = rq->core->core_pick_seq; /* Something should have been selected for current CPU */ WARN_ON_ONCE(!next); @@ -6517,7 +6568,10 @@ static bool try_steal_cookie(int this, int that) return false; do { - if (p == src->core_pick || p == src->curr) + if (p == src->core_pick || p == src->curr || p == src->donor) + goto next; + + if (task_is_blocked(p)) goto next; if (!is_cpu_allowed(p, this)) @@ -6820,6 +6874,34 @@ static void proxy_deactivate(struct rq *rq, struct task_struct *donor) block_task(rq, donor, state); } +/* + * Remove a retained proxy donor before changing its scheduler ownership. + * The caller holds p->pi_lock, so p cannot wake and migrate if block_task() + * drops it from the runqueue. If DELAY_DEQUEUE keeps a blocked fair task + * queued, switching_from_fair() completes the dequeue in the immediately + * following sched_change_begin(). + */ +void sched_proxy_block_task(struct rq *rq, struct task_struct *p) +{ + unsigned long state = READ_ONCE(p->__state); + + lockdep_assert_held(&p->pi_lock); + lockdep_assert_rq_held(rq); + + if (!p->is_blocked || !task_on_rq_queued(p)) + return; + if (WARN_ON_ONCE(state == TASK_RUNNING)) + return; + + if (task_current_donor(rq, p)) + proxy_reset_donor(rq); + + if (!p->se.sched_delayed) + block_task(rq, p, state); + + WARN_ON_ONCE(task_on_rq_queued(p) && !p->se.sched_delayed); +} + static inline void proxy_release_rq_lock(struct rq *rq, struct rq_flags *rf) __releases(__rq_lockp(rq)) { @@ -6865,9 +6947,9 @@ static void proxy_migrate_task(struct rq *rq, struct rq_flags *rf, __must_hold(__rq_lockp(rq)) { struct rq *target_rq = cpu_rq(target_cpu); + LIST_HEAD(migrate_list); lockdep_assert_rq_held(rq); - WARN_ON(p == rq->curr); /* * Since we are migrating a blocked donor, it could be rq->donor, * and we want to make sure there aren't any references from this @@ -6880,13 +6962,20 @@ static void proxy_migrate_task(struct rq *rq, struct rq_flags *rf, * before we release the lock. */ proxy_resched_idle(rq); - - deactivate_task(rq, p, DEQUEUE_NOCLOCK); - proxy_set_task_cpu(p, target_cpu); - + for (; p; p = p->blocked_donor) { + WARN_ON(p == rq->curr); + deactivate_task(rq, p, DEQUEUE_NOCLOCK); + proxy_set_task_cpu(p, target_cpu); + /* + * We can re-use se.group_node to migrate the thing, + * because @p is deactivated (won't be balanced) and + * we hold the rq_lock. + */ + list_add(&p->se.group_node, &migrate_list); + } proxy_release_rq_lock(rq, rf); - attach_one_task(target_rq, p); + __attach_tasks(target_rq, &migrate_list); proxy_reacquire_rq_lock(rq, rf); } @@ -6979,7 +7068,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) if (!READ_ONCE(owner->on_rq) || owner->se.sched_delayed) { /* XXX Don't handle blocked owners/delayed dequeue yet */ if (curr_in_chain) - return proxy_resched_idle(rq); + goto resched_idle; __clear_task_blocked_on(p, NULL); goto deactivate; } @@ -6991,7 +7080,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) * and leave that CPU to sort things out. */ if (curr_in_chain) - return proxy_resched_idle(rq); + goto resched_idle; goto migrate_task; } @@ -7004,7 +7093,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) * case we should end up back in find_proxy_task(), this time * hopefully with all relevant tasks already enqueued. */ - return proxy_resched_idle(rq); + goto resched_idle; } /* @@ -7041,7 +7130,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) * So schedule rq->idle so that ttwu_runnable() can get the rq * lock and mark owner as running. */ - return proxy_resched_idle(rq); + goto resched_idle; } /* * OK, now we're absolutely sure @owner is on this @@ -7051,8 +7140,18 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) owner->blocked_donor = p; } WARN_ON_ONCE(owner && !owner->on_rq); + + if (owner && !sched_cpu_cookie_match(rq, owner)) { + if (curr_in_chain) + return proxy_resched_idle(rq); + p = donor; /* Deactivate the donor, not the runnable owner */ + clear_task_blocked_on(p, NULL); + goto deactivate; + } return owner; +resched_idle: + return proxy_resched_idle(rq); deactivate: proxy_deactivate(rq, p); return NULL; @@ -7184,13 +7283,12 @@ static void __sched notrace __schedule(int sched_mode) } } else if (!preempt && prev_state) { /* - * We pass task_is_blocked() as the should_block arg - * in order to keep mutex-blocked tasks on the runqueue - * for slection with proxy-exec (without proxy-exec - * task_is_blocked() will always be false). + * Keep mutex-blocked tasks on the runqueue for proxy execution + * only when their scheduling class allows it. Without proxy + * execution, task_is_blocked() always returns false. */ try_to_block_task(rq, prev, &prev_state, - !task_is_blocked(prev)); + !task_is_blocked(prev) || !scx_allow_proxy_exec(prev)); switch_count = &prev->nvcsw; } @@ -7211,6 +7309,7 @@ pick_again: } if (next == rq->idle) { zap_balance_callbacks(rq); + scx_proxy_reenqueue_retry(rq, next); goto keep_resched; } } @@ -7229,8 +7328,10 @@ pick_again: * on_cpu. */ donor->sched_class->put_prev_task(rq, donor, donor); - donor->sched_class->set_next_task(rq, donor, true); + donor->sched_class->set_next_task(rq, donor, SNT_PICK); } + scx_proxy_donor_start(rq); + scx_proxy_reenqueue_retry(rq, next); } else { rq_set_donor(rq, next); } @@ -7489,27 +7590,6 @@ asmlinkage __visible void __sched notrace preempt_schedule(void) NOKPROBE_SYMBOL(preempt_schedule); EXPORT_SYMBOL(preempt_schedule); -#ifdef CONFIG_PREEMPT_DYNAMIC -# ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL -# ifndef preempt_schedule_dynamic_enabled -# define preempt_schedule_dynamic_enabled preempt_schedule -# define preempt_schedule_dynamic_disabled NULL -# endif -DEFINE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled); -EXPORT_STATIC_CALL_TRAMP(preempt_schedule); -# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) -static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule); -void __sched notrace dynamic_preempt_schedule(void) -{ - if (!static_branch_unlikely(&sk_dynamic_preempt_schedule)) - return; - preempt_schedule(); -} -NOKPROBE_SYMBOL(dynamic_preempt_schedule); -EXPORT_SYMBOL(dynamic_preempt_schedule); -# endif -#endif /* CONFIG_PREEMPT_DYNAMIC */ - /** * preempt_schedule_notrace - preempt_schedule called by tracing * @@ -7562,27 +7642,6 @@ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) } EXPORT_SYMBOL_GPL(preempt_schedule_notrace); -#ifdef CONFIG_PREEMPT_DYNAMIC -# if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) -# ifndef preempt_schedule_notrace_dynamic_enabled -# define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace -# define preempt_schedule_notrace_dynamic_disabled NULL -# endif -DEFINE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled); -EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace); -# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) -static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule_notrace); -void __sched notrace dynamic_preempt_schedule_notrace(void) -{ - if (!static_branch_unlikely(&sk_dynamic_preempt_schedule_notrace)) - return; - preempt_schedule_notrace(); -} -NOKPROBE_SYMBOL(dynamic_preempt_schedule_notrace); -EXPORT_SYMBOL(dynamic_preempt_schedule_notrace); -# endif -#endif - #endif /* CONFIG_PREEMPTION */ /* @@ -7799,7 +7858,7 @@ out_unlock: } #endif /* CONFIG_RT_MUTEXES */ -#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) +#if !defined(CONFIG_PREEMPTION) int __sched __cond_resched(void) { if (should_resched(0) && !irqs_disabled()) { @@ -7827,38 +7886,6 @@ int __sched __cond_resched(void) EXPORT_SYMBOL(__cond_resched); #endif -#ifdef CONFIG_PREEMPT_DYNAMIC -# ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL -# define cond_resched_dynamic_enabled __cond_resched -# define cond_resched_dynamic_disabled ((void *)&__static_call_return0) -DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched); -EXPORT_STATIC_CALL_TRAMP(cond_resched); - -# define might_resched_dynamic_enabled __cond_resched -# define might_resched_dynamic_disabled ((void *)&__static_call_return0) -DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched); -EXPORT_STATIC_CALL_TRAMP(might_resched); -# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) -static DEFINE_STATIC_KEY_FALSE(sk_dynamic_cond_resched); -int __sched dynamic_cond_resched(void) -{ - if (!static_branch_unlikely(&sk_dynamic_cond_resched)) - return 0; - return __cond_resched(); -} -EXPORT_SYMBOL(dynamic_cond_resched); - -static DEFINE_STATIC_KEY_FALSE(sk_dynamic_might_resched); -int __sched dynamic_might_resched(void) -{ - if (!static_branch_unlikely(&sk_dynamic_might_resched)) - return 0; - return __cond_resched(); -} -EXPORT_SYMBOL(dynamic_might_resched); -# endif -#endif /* CONFIG_PREEMPT_DYNAMIC */ - /* * __cond_resched_lock() - if a reschedule is pending, drop the given lock, * call schedule, and on return reacquire the lock. @@ -7928,50 +7955,21 @@ EXPORT_SYMBOL(__cond_resched_rwlock_write); # endif /* - * SC:cond_resched - * SC:might_resched - * SC:preempt_schedule - * SC:preempt_schedule_notrace - * SC:irqentry_exit_cond_resched - * - * * NONE: - * cond_resched <- __cond_resched - * might_resched <- RET0 - * preempt_schedule <- NOP - * preempt_schedule_notrace <- NOP - * irqentry_exit_cond_resched <- NOP - * dynamic_preempt_lazy <- false + * (unselectable) * * VOLUNTARY: - * cond_resched <- __cond_resched - * might_resched <- __cond_resched - * preempt_schedule <- NOP - * preempt_schedule_notrace <- NOP - * irqentry_exit_cond_resched <- NOP - * dynamic_preempt_lazy <- false + * (unselectable) * * FULL: - * cond_resched <- RET0 - * might_resched <- RET0 - * preempt_schedule <- preempt_schedule - * preempt_schedule_notrace <- preempt_schedule_notrace - * irqentry_exit_cond_resched <- irqentry_exit_cond_resched * dynamic_preempt_lazy <- false * * LAZY: - * cond_resched <- RET0 - * might_resched <- RET0 - * preempt_schedule <- preempt_schedule - * preempt_schedule_notrace <- preempt_schedule_notrace - * irqentry_exit_cond_resched <- irqentry_exit_cond_resched * dynamic_preempt_lazy <- true */ enum { preempt_dynamic_undefined = -1, - preempt_dynamic_none, - preempt_dynamic_voluntary, preempt_dynamic_full, preempt_dynamic_lazy, }; @@ -7980,21 +7978,11 @@ int preempt_dynamic_mode = preempt_dynamic_undefined; int sched_dynamic_mode(const char *str) { -# if !(defined(CONFIG_PREEMPT_RT) || defined(CONFIG_ARCH_HAS_PREEMPT_LAZY)) - if (!strcmp(str, "none")) - return preempt_dynamic_none; - - if (!strcmp(str, "voluntary")) - return preempt_dynamic_voluntary; -# endif - if (!strcmp(str, "full")) return preempt_dynamic_full; -# ifdef CONFIG_ARCH_HAS_PREEMPT_LAZY if (!strcmp(str, "lazy")) return preempt_dynamic_lazy; -# endif return -EINVAL; } @@ -8002,71 +7990,18 @@ int sched_dynamic_mode(const char *str) # define preempt_dynamic_key_enable(f) static_key_enable(&sk_dynamic_##f.key) # define preempt_dynamic_key_disable(f) static_key_disable(&sk_dynamic_##f.key) -# if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) -# define preempt_dynamic_enable(f) static_call_update(f, f##_dynamic_enabled) -# define preempt_dynamic_disable(f) static_call_update(f, f##_dynamic_disabled) -# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) -# define preempt_dynamic_enable(f) preempt_dynamic_key_enable(f) -# define preempt_dynamic_disable(f) preempt_dynamic_key_disable(f) -# else -# error "Unsupported PREEMPT_DYNAMIC mechanism" -# endif - static DEFINE_MUTEX(sched_dynamic_mutex); static void __sched_dynamic_update(int mode) { - /* - * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in - * the ZERO state, which is invalid. - */ - preempt_dynamic_enable(cond_resched); - preempt_dynamic_enable(might_resched); - preempt_dynamic_enable(preempt_schedule); - preempt_dynamic_enable(preempt_schedule_notrace); - preempt_dynamic_enable(irqentry_exit_cond_resched); - preempt_dynamic_key_disable(preempt_lazy); - switch (mode) { - case preempt_dynamic_none: - preempt_dynamic_enable(cond_resched); - preempt_dynamic_disable(might_resched); - preempt_dynamic_disable(preempt_schedule); - preempt_dynamic_disable(preempt_schedule_notrace); - preempt_dynamic_disable(irqentry_exit_cond_resched); - preempt_dynamic_key_disable(preempt_lazy); - if (mode != preempt_dynamic_mode) - pr_info("Dynamic Preempt: none\n"); - break; - - case preempt_dynamic_voluntary: - preempt_dynamic_enable(cond_resched); - preempt_dynamic_enable(might_resched); - preempt_dynamic_disable(preempt_schedule); - preempt_dynamic_disable(preempt_schedule_notrace); - preempt_dynamic_disable(irqentry_exit_cond_resched); - preempt_dynamic_key_disable(preempt_lazy); - if (mode != preempt_dynamic_mode) - pr_info("Dynamic Preempt: voluntary\n"); - break; - case preempt_dynamic_full: - preempt_dynamic_disable(cond_resched); - preempt_dynamic_disable(might_resched); - preempt_dynamic_enable(preempt_schedule); - preempt_dynamic_enable(preempt_schedule_notrace); - preempt_dynamic_enable(irqentry_exit_cond_resched); preempt_dynamic_key_disable(preempt_lazy); if (mode != preempt_dynamic_mode) pr_info("Dynamic Preempt: full\n"); break; case preempt_dynamic_lazy: - preempt_dynamic_disable(cond_resched); - preempt_dynamic_disable(might_resched); - preempt_dynamic_enable(preempt_schedule); - preempt_dynamic_enable(preempt_schedule_notrace); - preempt_dynamic_enable(irqentry_exit_cond_resched); preempt_dynamic_key_enable(preempt_lazy); if (mode != preempt_dynamic_mode) pr_info("Dynamic Preempt: lazy\n"); @@ -8099,11 +8034,7 @@ __setup("preempt=", setup_preempt_mode); static void __init preempt_dynamic_init(void) { if (preempt_dynamic_mode == preempt_dynamic_undefined) { - if (IS_ENABLED(CONFIG_PREEMPT_NONE)) { - sched_dynamic_update(preempt_dynamic_none); - } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) { - sched_dynamic_update(preempt_dynamic_voluntary); - } else if (IS_ENABLED(CONFIG_PREEMPT_LAZY)) { + if (IS_ENABLED(CONFIG_PREEMPT_LAZY)) { sched_dynamic_update(preempt_dynamic_lazy); } else { /* Default static call setting, nothing to do */ @@ -8123,8 +8054,6 @@ static void __init preempt_dynamic_init(void) } \ EXPORT_SYMBOL_GPL(preempt_model_##mode) -PREEMPT_MODEL_ACCESSOR(none); -PREEMPT_MODEL_ACCESSOR(voluntary); PREEMPT_MODEL_ACCESSOR(full); PREEMPT_MODEL_ACCESSOR(lazy); @@ -8137,7 +8066,7 @@ static inline void preempt_dynamic_init(void) { } #endif /* CONFIG_PREEMPT_DYNAMIC */ const char *preempt_modes[] = { - "none", "voluntary", "full", "lazy", NULL, + "full", "lazy", NULL, }; const char *preempt_model_str(void) @@ -8759,6 +8688,9 @@ int sched_cpu_activate(unsigned int cpu) */ sched_set_rq_online(rq, cpu); + /* preferred is subset of active and follows its state */ + set_cpu_preferred(cpu, true); + return 0; } @@ -8772,6 +8704,8 @@ int sched_cpu_deactivate(unsigned int cpu) if (ret) return ret; + set_cpu_preferred(cpu, false); + /* * Remove CPU from nohz.idle_cpus_mask to prevent participating in * load balancing when not active @@ -11349,3 +11283,88 @@ void sched_change_end(struct sched_change_ctx *ctx) p->sched_class->prio_changed(rq, p, ctx->prio); } } + +#ifdef CONFIG_PREFERRED_CPU +static DEFINE_PER_CPU(struct cpu_stop_work, npc_push_task_work); + +static int sched_non_preferred_cpu_push_stop(void *arg) +{ + struct task_struct *p = arg; + struct rq *rq = this_rq(); + struct rq_flags rf; + int cpu; + + if (cpu_preferred(rq->cpu)) { + scoped_guard(rq_lock_irqsave, rq) + rq->npc_push_work_pending = false; + put_task_struct(p); + return 0; + } + + scoped_guard (raw_spinlock_irq, &p->pi_lock) { + /* + * select_fallback_rq() may acquire the rq lock in case of + * fallback. So call it before grabbing rq lock. If the task + * migrates to another CPU before the rq lock is acquired, + * subsequent validation of task's current rq will help to + * safely bail out. + */ + cpu = select_fallback_rq(rq->cpu, p); + context_unsafe_alias(rq); + rq_lock(rq, &rf); + rq->npc_push_work_pending = false; + update_rq_clock(rq); + + if (task_rq(p) == rq && task_on_rq_queued(p)) { + struct rq *dest_rq = __migrate_task(rq, &rf, p, cpu); + + if (rq != dest_rq) + schedstat_inc(p->stats.nr_migrations_cpu_non_preferred); + rq = dest_rq; + } + rq_unlock(rq, &rf); + } + + put_task_struct(p); + return 0; +} + +/* + * Push the current task running on non-preferred CPU(npc). + * Using this non preferred CPU will lead to more contention + * in the host. So it is better not to use this CPU. + * + * Since task is running, call a stopper to push the task out. This is + * similar to how task moves during hotplug. In select_fallback_rq() a + * preferred CPU will be chosen and henceforth task shouldn't come back to + * this CPU again. + * + * Works for FAIR class only. + * + * If task is affined only on non-preferred CPUs, no point in moving it out. + */ +void sched_push_current_non_preferred_cpu(struct rq *rq) +{ + struct task_struct *push_task = rq->curr; + + scoped_guard(rq_lock, rq) { + /* Push the task if its explicit affinity allows */ + if (!task_can_migrate_to_preferred(push_task, rq->cpu)) + return; + + /* There is already a stopper thread. Don't race with it. */ + if (rq->npc_push_work_pending) + return; + + if (is_migration_disabled(push_task)) + return; + + rq->npc_push_work_pending = true; + } + + /* sched_tick runs with interrupts disabled. */ + get_task_struct(push_task); + stop_one_cpu_nowait(rq->cpu, sched_non_preferred_cpu_push_stop, + push_task, this_cpu_ptr(&npc_push_task_work)); +} +#endif diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 06bddaa738e5..f16970ca81d0 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -255,7 +255,7 @@ void __account_forceidle_time(struct task_struct *p, u64 delta) * occasion account more time than the calling functions think elapsed. */ #ifdef CONFIG_PARAVIRT -struct static_key paravirt_steal_enabled; +DEFINE_STATIC_KEY_FALSE(paravirt_steal_enabled); #ifdef CONFIG_HAVE_PV_STEAL_CLOCK_GEN static u64 native_steal_clock(int cpu) @@ -270,7 +270,7 @@ DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock); static __always_inline u64 steal_account_process_time(u64 maxtime) { #ifdef CONFIG_PARAVIRT - if (static_key_false(¶virt_steal_enabled)) { + if (static_branch_unlikely(¶virt_steal_enabled)) { u64 steal; steal = paravirt_steal_clock(smp_processor_id()); diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 0663c00c41c0..c0ebdcde5fe5 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1097,7 +1097,7 @@ static int start_dl_timer(struct sched_dl_entity *dl_se) * chosen as the deadline is too small, don't even try to * start the timer in the past! */ - if (ktime_us_delta(act, now) < 0) + if (ktime_before(act, now)) return 0; /* @@ -2773,11 +2773,14 @@ static void start_hrtick_dl(struct rq *rq, struct sched_dl_entity *dl_se) * DL keeps current in tree, because ->deadline is not typically changed while * a task is runnable. */ -static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first) +static void set_next_task_dl(struct rq *rq, struct task_struct *p, enum snt_e type) { struct sched_dl_entity *dl_se = &p->dl; struct dl_rq *dl_rq = &rq->dl; + if (type == SNT_REPICK) + return; + p->se.exec_start = rq_clock_task(rq); if (on_dl_rq(&p->dl)) update_stats_wait_end_dl(dl_rq, dl_se); @@ -2788,7 +2791,7 @@ static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first) WARN_ON_ONCE(dl_rq->curr); dl_rq->curr = dl_se; - if (!first) + if (type != SNT_PICK) return; if (rq->donor->sched_class != &dl_sched_class) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 72236db67983..e6a3b516c703 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -73,13 +73,13 @@ static int sched_feat_show(struct seq_file *m, void *v) #ifdef CONFIG_JUMP_LABEL -#define jump_label_key__true STATIC_KEY_INIT_TRUE -#define jump_label_key__false STATIC_KEY_INIT_FALSE +#define jump_label_key__true { .key_true = STATIC_KEY_TRUE_INIT } +#define jump_label_key__false { .key_false = STATIC_KEY_FALSE_INIT } #define SCHED_FEAT(name, enabled) \ jump_label_key__##enabled , -struct static_key sched_feat_keys[__SCHED_FEAT_NR] = { +union sched_feat_key sched_feat_keys[__SCHED_FEAT_NR] = { #include "features.h" }; @@ -87,12 +87,12 @@ struct static_key sched_feat_keys[__SCHED_FEAT_NR] = { static void sched_feat_disable(int i) { - static_key_disable_cpuslocked(&sched_feat_keys[i]); + static_branch_disable_cpuslocked(&sched_feat_keys[i].key_true); } static void sched_feat_enable(int i) { - static_key_enable_cpuslocked(&sched_feat_keys[i]); + static_branch_enable_cpuslocked(&sched_feat_keys[i].key_false); } #else /* !CONFIG_JUMP_LABEL: */ static void sched_feat_disable(int i) { }; @@ -280,16 +280,10 @@ static ssize_t sched_dynamic_write(struct file *filp, const char __user *ubuf, static int sched_dynamic_show(struct seq_file *m, void *v) { - int i = (IS_ENABLED(CONFIG_PREEMPT_RT) || IS_ENABLED(CONFIG_ARCH_HAS_PREEMPT_LAZY)) * 2; int mode = READ_ONCE(preempt_dynamic_mode); - int j; - /* Count entries in NULL terminated preempt_modes */ - for (j = 0; preempt_modes[j]; j++) - ; - j -= !IS_ENABLED(CONFIG_ARCH_HAS_PREEMPT_LAZY); - - for (; i < j; i++) { + /* Stop at NULL terminator */ + for (int i = 0; preempt_modes[i]; i++) { if (mode == i) seq_puts(m, "("); seq_puts(m, preempt_modes[i]); @@ -1446,6 +1440,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns, P_SCHEDSTAT(nr_failed_migrations_running); P_SCHEDSTAT(nr_failed_migrations_hot); P_SCHEDSTAT(nr_forced_migrations); + P_SCHEDSTAT(nr_migrations_cpu_non_preferred); P_SCHEDSTAT(nr_wakeups); P_SCHEDSTAT(nr_wakeups_sync); P_SCHEDSTAT(nr_wakeups_migrate); diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 5fe980da545d..522cf6e98e31 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -24,6 +24,11 @@ DEFINE_RAW_SPINLOCK(scx_sched_lock); +bool scx_allow_proxy_exec(const struct task_struct *p) +{ + return true; +} + /* * NOTE: sched_ext is in the process of growing multiple scheduler support and * scx_root usage is in a transitional state. Naked dereferences are safe if the @@ -1087,6 +1092,10 @@ static void schedule_deferred_locked(struct rq *rq) schedule_deferred(rq); } +void scx_proxy_reenqueue_retry(struct rq *rq, struct task_struct *next) +{ +} + void schedule_dsq_reenq(struct scx_sched *sch, struct scx_dispatch_q *dsq, u64 reenq_flags, struct rq *locked_rq) { @@ -3031,10 +3040,13 @@ has_tasks: return verdict; } -static void set_next_task_scx(struct rq *rq, struct task_struct *p, bool first) +static void set_next_task_scx(struct rq *rq, struct task_struct *p, enum snt_e type) { struct scx_sched *sch = scx_task_sched(p); + if (type == SNT_REPICK) + return; + if (p->scx.flags & SCX_TASK_QUEUED) { /* * Core-sched might decide to execute @p before it is @@ -3092,6 +3104,10 @@ static void set_next_task_scx(struct rq *rq, struct task_struct *p, bool first) } } +void scx_proxy_donor_start(struct rq *rq) +{ +} + static enum scx_cpu_preempt_reason preempt_reason_from_class(const struct sched_class *class) { diff --git a/kernel/sched/ext/ext.h b/kernel/sched/ext/ext.h index 0b7fc46aee08..3cfbfeb1bf9d 100644 --- a/kernel/sched/ext/ext.h +++ b/kernel/sched/ext/ext.h @@ -20,6 +20,9 @@ void scx_rq_deactivate(struct rq *rq); int scx_check_setscheduler(struct task_struct *p, int policy); bool task_should_scx(int policy); bool scx_allow_ttwu_queue(const struct task_struct *p); +bool scx_allow_proxy_exec(const struct task_struct *p); +void scx_proxy_donor_start(struct rq *rq); +void scx_proxy_reenqueue_retry(struct rq *rq, struct task_struct *next); void init_sched_ext_class(void); static inline u32 scx_cpuperf_target(s32 cpu) @@ -54,6 +57,10 @@ static inline void scx_rq_deactivate(struct rq *rq) {} static inline int scx_check_setscheduler(struct task_struct *p, int policy) { return 0; } static inline bool task_on_scx(const struct task_struct *p) { return false; } static inline bool scx_allow_ttwu_queue(const struct task_struct *p) { return true; } +static inline bool scx_allow_proxy_exec(const struct task_struct *p) { return true; } +static inline void scx_proxy_donor_start(struct rq *rq) {} +static inline void scx_proxy_reenqueue_retry(struct rq *rq, + struct task_struct *next) {} static inline void init_sched_ext_class(void) {} #endif /* CONFIG_SCHED_CLASS_EXT */ diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 57360f5cdde4..5c98d8dfce5d 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -24,6 +24,7 @@ #include <linux/mmap_lock.h> #include <linux/hugetlb_inline.h> #include <linux/jiffies.h> +#include <linux/math.h> #include <linux/mm_api.h> #include <linux/highmem.h> #include <linux/hrtimer.h> @@ -820,12 +821,6 @@ static u64 ineligible_vruntime(struct cfs_rq *cfs_rq) if (curr && !curr->on_rq) curr = NULL; - /* - * This is called from set_next_task_fair(.first=true) / - * set_protect_slice() so curr had better be set and on_rq. - */ - WARN_ON_ONCE(!curr); - if (weight) { s64 runtime = cfs_rq->sum_w_vruntime; @@ -1137,10 +1132,9 @@ static inline void set_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity /* If there are shorter slices than se's one */ if (slice != se->slice) { + vprot = min_vruntime(vprot, se->vruntime + calc_delta_fair(slice, se)); if (sched_feat(PREEMPT_SHORT)) vprot = min_vruntime(vprot, ineligible_vruntime(cfs_rq)); - else - vprot = min_vruntime(vprot, se->vruntime + calc_delta_fair(slice, se)); } se->vprot = vprot; @@ -1148,10 +1142,19 @@ static inline void set_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity static inline void update_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) { - u64 slice = cfs_rq_min_slice(cfs_rq); u64 vruntime = min_vruntime(se->vruntime, avg_vruntime(cfs_rq)); + u64 slice = normalized_sysctl_sched_base_slice; + u64 vprot; - se->vprot = min_vruntime(se->vprot, vruntime + calc_delta_fair(slice, se)); + if (sched_feat(RUN_TO_PARITY)) + slice = cfs_rq_min_slice(cfs_rq); + + vprot = min_vruntime(se->vprot, vruntime + calc_delta_fair(slice, se)); + + if (sched_feat(PREEMPT_SHORT) && slice != se->slice) + vprot = min_vruntime(vprot, ineligible_vruntime(cfs_rq)); + + se->vprot = vprot; } static inline bool protect_slice(struct sched_entity *se) @@ -3713,7 +3716,7 @@ static void update_task_scan_period(struct task_struct *p, p->mm->numa_next_scan = jiffies + msecs_to_jiffies(p->numa_scan_period); - return; + goto out; } /* @@ -3757,7 +3760,10 @@ static void update_task_scan_period(struct task_struct *p, p->numa_scan_period = clamp(p->numa_scan_period + diff, task_scan_min(p), task_scan_max(p)); - memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); + +out: + memset(p->numa_faults_locality, 0, + sizeof(p->numa_faults_locality)); } /* @@ -8209,7 +8215,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = &rq->cfs; unsigned long weight; - bool curr; if (task_is_throttled(p) && enqueue_throttled_task(p)) return; @@ -8238,23 +8243,14 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) if (p->in_iowait) cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT); - /* - * XXX comment on the curr thing - */ - curr = (cfs_rq->curr == se); - if (curr) - place_entity(cfs_rq, se, flags); if (se->on_rq && se->sched_delayed) requeue_delayed_entity(cfs_rq, se); weight = enqueue_hierarchy(p, flags); - - if (!curr) { - reweight_eevdf(cfs_rq, se, weight, false); - place_entity(cfs_rq, se, flags | ENQUEUE_QUEUED); - __enqueue_entity(cfs_rq, se); - } + reweight_eevdf(cfs_rq, se, weight, false); + place_entity(cfs_rq, se, flags | ENQUEUE_QUEUED); + __enqueue_entity(cfs_rq, se); if (!rq_h_nr_queued && rq->cfs.h_nr_queued) dl_server_start(&rq->fair_server); @@ -8674,8 +8670,8 @@ static int sched_balance_find_dst_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) { unsigned long load, min_load = ULONG_MAX; - unsigned int min_exit_latency = UINT_MAX; - u64 latest_idle_timestamp = 0; + u64 min_exit_latency = U64_MAX; + unsigned int nr_candidates = 0; int least_loaded_cpu = this_cpu; int shallowest_idle_cpu = -1; int i; @@ -8696,24 +8692,16 @@ sched_balance_find_dst_group_cpu(struct sched_group *group, struct task_struct * if (available_idle_cpu(i)) { struct cpuidle_state *idle = idle_get_state(rq); - if (idle && idle->exit_latency < min_exit_latency) { - /* - * We give priority to a CPU whose idle state - * has the smallest exit latency irrespective - * of any idle timestamp. - */ - min_exit_latency = idle->exit_latency; - latest_idle_timestamp = rq->idle_stamp; - shallowest_idle_cpu = i; - } else if ((!idle || idle->exit_latency == min_exit_latency) && - rq->idle_stamp > latest_idle_timestamp) { - /* - * If equal or no active idle state, then - * the most recently idled CPU might have - * a warmer cache. - */ - latest_idle_timestamp = rq->idle_stamp; + u64 exit_latency = idle ? idle->exit_latency : U64_MAX; + + if (shallowest_idle_cpu == -1 || exit_latency < min_exit_latency) { + min_exit_latency = exit_latency; shallowest_idle_cpu = i; + nr_candidates = 1; + } else if (exit_latency == min_exit_latency) { + nr_candidates++; + if (!reciprocal_scale(sched_rng(), nr_candidates)) + shallowest_idle_cpu = i; } } else if (shallowest_idle_cpu == -1) { load = cpu_load(cpu_rq(i)); @@ -8812,6 +8800,35 @@ static inline bool test_idle_cores(int cpu) } /* + * Redirect a CPU to a higher-priority available sibling in its SMT domain, + * subject to task affinity. + */ +static inline int select_idle_smt_cpu(struct task_struct *p, int cpu) +{ + struct sched_domain *sd; + int best = cpu; + int sibling; + + if (!sched_smt_active()) + return cpu; + + sd = rcu_dereference_all(cpu_rq(cpu)->sd); + if (!sd || !(sd->flags & SD_SHARE_CPUCAPACITY) || + !(sd->flags & SD_ASYM_PACKING)) + return cpu; + + for_each_cpu_and(sibling, sched_domain_span(sd), p->cpus_ptr) { + if (sibling == best || !choose_idle_cpu(sibling, p)) + continue; + + if (sched_asym_prefer(sibling, best)) + best = sibling; + } + + return best; +} + +/* * Scans the local SMT mask to see if the entire core is idle, and records this * information in sd_balance_shared->has_idle_cores. * @@ -9195,7 +9212,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) if (choose_idle_cpu(target, p) && asym_fits_cpu(task_util, util_min, util_max, target)) - return target; + goto select_smt_priority; /* * If the previous CPU is cache affine and idle, don't be stupid: @@ -9205,8 +9222,10 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) asym_fits_cpu(task_util, util_min, util_max, prev)) { if (!static_branch_unlikely(&sched_cluster_active) || - cpus_share_resources(prev, target)) - return prev; + cpus_share_resources(prev, target)) { + target = prev; + goto select_smt_priority; + } prev_aff = prev; } @@ -9224,7 +9243,8 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) prev == smp_processor_id() && this_rq()->nr_running <= 1 && asym_fits_cpu(task_util, util_min, util_max, prev)) { - return prev; + target = prev; + goto select_smt_priority; } /* Check a recently used CPU as a potential idle candidate: */ @@ -9238,8 +9258,10 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) asym_fits_cpu(task_util, util_min, util_max, recent_used_cpu)) { if (!static_branch_unlikely(&sched_cluster_active) || - cpus_share_resources(recent_used_cpu, target)) - return recent_used_cpu; + cpus_share_resources(recent_used_cpu, target)) { + target = recent_used_cpu; + goto select_smt_priority; + } } else { recent_used_cpu = -1; @@ -9261,7 +9283,11 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) */ if (sd) { i = select_idle_capacity(p, sd, target); - return ((unsigned)i < nr_cpumask_bits) ? i : target; + if ((unsigned int)i < nr_cpumask_bits) { + target = i; + goto select_smt_priority; + } + return target; } } @@ -9274,14 +9300,18 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) if (!has_idle_core && cpus_share_cache(prev, target)) { i = select_idle_smt(p, sd, prev); - if ((unsigned int)i < nr_cpumask_bits) - return i; + if ((unsigned int)i < nr_cpumask_bits) { + target = i; + goto select_smt_priority; + } } } i = select_idle_cpu(p, sd, has_idle_core, target); - if ((unsigned)i < nr_cpumask_bits) - return i; + if ((unsigned int)i < nr_cpumask_bits) { + target = i; + goto select_smt_priority; + } /* * For cluster machines which have lower sharing cache like L2 or @@ -9289,12 +9319,19 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) * first. But prev_cpu or recent_used_cpu may also be a good candidate, * use them if possible when no idle CPU found in select_idle_cpu(). */ - if ((unsigned int)prev_aff < nr_cpumask_bits) - return prev_aff; - if ((unsigned int)recent_used_cpu < nr_cpumask_bits) - return recent_used_cpu; + if ((unsigned int)prev_aff < nr_cpumask_bits) { + target = prev_aff; + goto select_smt_priority; + } + if ((unsigned int)recent_used_cpu < nr_cpumask_bits) { + target = recent_used_cpu; + goto select_smt_priority; + } return target; + +select_smt_priority: + return select_idle_smt_cpu(p, target); } /** @@ -9971,8 +10008,10 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) } /* Slow path */ - if (unlikely(sd)) - return sched_balance_find_dst_cpu(sd, p, cpu, prev_cpu, sd_flag); + if (unlikely(sd)) { + new_cpu = sched_balance_find_dst_cpu(sd, p, cpu, prev_cpu, sd_flag); + return select_idle_smt_cpu(p, new_cpu); + } /* Fast path */ if (wake_flags & WF_TTWU) @@ -10072,8 +10111,14 @@ static inline bool set_preempt_buddy(struct cfs_rq *cfs_rq, struct sched_entity static inline bool set_short_buddy(struct cfs_rq *cfs_rq, struct sched_entity *pse) { - if (cfs_rq->next && cfs_rq->next->slice < pse->slice) - return false; + if (cfs_rq->next) { + if (cfs_rq->next->slice < pse->slice) + return false; + + if (cfs_rq->next->slice == pse->slice && + entity_before(cfs_rq->next, pse)) + return false; + } set_next_buddy(cfs_rq, pse); return true; @@ -11439,21 +11484,7 @@ next: */ static void attach_tasks(struct lb_env *env) { - struct list_head *tasks = &env->tasks; - struct task_struct *p; - struct rq_flags rf; - - rq_lock(env->dst_rq, &rf); - update_rq_clock(env->dst_rq); - - while (!list_empty(tasks)) { - p = list_first_entry(tasks, struct task_struct, se.group_node); - list_del_init(&p->se.group_node); - - attach_task(env->dst_rq, p); - } - - rq_unlock(env->dst_rq, &rf); + __attach_tasks(env->dst_rq, &env->tasks); } #ifdef CONFIG_NO_HZ_COMMON @@ -13746,7 +13777,7 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq, }; bool need_unlock = false; - cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); + cpumask_and(cpus, sched_domain_span(sd), cpu_preferred_mask); schedstat_inc(sd->lb_count[idle]); @@ -14871,10 +14902,8 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf) */ this_rq->idle_stamp = rq_clock(this_rq); - /* - * Do not pull tasks towards !active CPUs... - */ - if (!cpu_active(this_cpu)) + /* Do not pull tasks towards !preferred CPUs */ + if (!cpu_preferred(this_cpu)) return 0; /* @@ -15514,14 +15543,18 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p) } } -static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first) +static void set_next_task_fair(struct rq *rq, struct task_struct *p, enum snt_e type) { struct sched_entity *se = &p->se; - bool throttled = false; struct cfs_rq *cfs_rq = &rq->cfs; unsigned long weight = NICE_0_LOAD; + bool first = type == SNT_PICK; + bool throttled = false; bool on_rq = se->on_rq; + if (type == SNT_REPICK) + goto repick; + clear_buddies(cfs_rq, se); if (on_rq) @@ -15565,11 +15598,18 @@ static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first) WARN_ON_ONCE(se->sched_delayed); - if (hrtick_enabled_fair(rq)) - hrtick_start_fair(rq, p); - update_misfit_status(p, rq); sched_fair_update_stop_tick(rq, p); + +repick: + /* + * A same-task repick skips put_prev_task_fair(), but + * pick_task_fair() refreshed the entity hrtick_start_fair() reads + * before selecting it again. rq->cfs.curr identifies that entity, + * including with group scheduling. + */ + if (hrtick_enabled_fair(rq)) + hrtick_start_fair(rq, p); } void init_cfs_rq(struct cfs_rq *cfs_rq) diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index eb73b65ce6c4..76f3c84ca684 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -487,8 +487,11 @@ static void put_prev_task_idle(struct rq *rq, struct task_struct *prev, struct t update_rq_avg_idle(rq); } -static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first) +static void set_next_task_idle(struct rq *rq, struct task_struct *next, enum snt_e type) { + if (type == SNT_REPICK) + return; + update_idle_core(rq); scx_update_idle(rq, true, true); schedstat_inc(rq->sched_goidle); diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 85303add726d..1535046a23ff 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1654,11 +1654,14 @@ static void wakeup_preempt_rt(struct rq *rq, struct task_struct *p, int flags) check_preempt_equal_prio(rq, p); } -static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool first) +static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, enum snt_e type) { struct sched_rt_entity *rt_se = &p->rt; struct rt_rq *rt_rq = &rq->rt; + if (type == SNT_REPICK) + return; + p->se.exec_start = rq_clock_task(rq); if (on_rt_rq(&p->rt)) update_stats_wait_end_rt(rt_rq, rt_se); @@ -1666,7 +1669,7 @@ static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool f /* The running task is never eligible for pushing */ dequeue_pushable_task(rq, p); - if (!first) + if (type != SNT_PICK) return; /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 4c25fbe84fb5..499a5649582e 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1325,6 +1325,9 @@ struct rq { #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING u64 prev_steal_time_rq; #endif +#ifdef CONFIG_PREFERRED_CPU + bool npc_push_work_pending; +#endif /* calc_load related fields */ unsigned long calc_load_update; @@ -1370,7 +1373,6 @@ struct rq { struct task_struct *core_pick; struct sched_dl_entity *core_dl_server; unsigned int core_enabled; - unsigned int core_sched_seq; struct rb_root core_tree; /* shared state -- careful with sched_core_cpu_deactivate() */ @@ -2446,16 +2448,25 @@ extern __read_mostly unsigned int sysctl_sched_features; #ifdef CONFIG_JUMP_LABEL -#define SCHED_FEAT(name, enabled) \ -static __always_inline bool static_branch_##name(struct static_key *key) \ -{ \ - return static_key_##enabled(key); \ +union sched_feat_key { + struct static_key_true key_true; + struct static_key_false key_false; +}; + +#define sched_feat_branch_true(key) static_branch_likely(&(key)->key_true) +#define sched_feat_branch_false(key) static_branch_unlikely(&(key)->key_false) + +#define SCHED_FEAT(name, enabled) \ +static __always_inline bool \ +static_branch_##name(union sched_feat_key *key) \ +{ \ + return sched_feat_branch_##enabled(key); \ } #include "features.h" #undef SCHED_FEAT -extern struct static_key sched_feat_keys[__SCHED_FEAT_NR]; +extern union sched_feat_key sched_feat_keys[__SCHED_FEAT_NR]; #define sched_feat(x) (static_branch_##x(&sched_feat_keys[__SCHED_FEAT_##x])) #else /* !CONFIG_JUMP_LABEL: */ @@ -2507,6 +2518,12 @@ static inline bool task_is_blocked(struct task_struct *p) return !!p->blocked_on; } +#ifdef CONFIG_SCHED_PROXY_EXEC +void sched_proxy_block_task(struct rq *rq, struct task_struct *p); +#else +static inline void sched_proxy_block_task(struct rq *rq, struct task_struct *p) {} +#endif + static inline int task_on_cpu(struct rq *rq, struct task_struct *p) { return p->on_cpu; @@ -2526,11 +2543,17 @@ static inline int task_on_rq_migrating(struct task_struct *p) #define WF_EXEC 0x02 /* Wakeup after exec; maps to SD_BALANCE_EXEC */ #define WF_FORK 0x04 /* Wakeup after fork; maps to SD_BALANCE_FORK */ #define WF_TTWU 0x08 /* Wakeup; maps to SD_BALANCE_WAKE */ - -#define WF_SYNC 0x10 /* Waker goes to sleep after wakeup */ +/* + * Hint that the caller expects the waker to sleep soon. + * Scheduler classes may use it for placement or preemption. + * Callers must not rely on it to prevent migration, + * preserve CPU locality or make the wakee run next. + */ +#define WF_SYNC 0x10 #define WF_MIGRATED 0x20 /* Internal use, task got migrated */ #define WF_CURRENT_CPU 0x40 /* Prefer to move the wakee to the current CPU. */ #define WF_RQ_SELECTED 0x80 /* ->select_task_rq() was called */ +#define WF_TTWU_RQ 0x100 /* Wakeup completed through ttwu_runnable() */ static_assert(WF_EXEC == SD_BALANCE_EXEC); static_assert(WF_FORK == SD_BALANCE_FORK); @@ -2620,6 +2643,12 @@ struct affinity_context { extern s64 update_curr_common(struct rq *rq); +enum snt_e { + SNT_NORMAL, /* set_next_task() */ + SNT_PICK, /* put_prev_set_next_task(): prev != next */ + SNT_REPICK, /* put_prev_set_next_task(): prev == next */ +}; + struct sched_class { #ifdef CONFIG_UCLAMP_TASK @@ -2677,7 +2706,7 @@ struct sched_class { * __schedule: rq->lock */ void (*put_prev_task)(struct rq *rq, struct task_struct *p, struct task_struct *next); - void (*set_next_task)(struct rq *rq, struct task_struct *p, bool first); + void (*set_next_task)(struct rq *rq, struct task_struct *p, enum snt_e type); /* * select_task_rq: p->pi_lock @@ -2780,7 +2809,7 @@ static inline void put_prev_task(struct rq *rq, struct task_struct *prev) static inline void set_next_task(struct rq *rq, struct task_struct *next) { - next->sched_class->set_next_task(rq, next, false); + next->sched_class->set_next_task(rq, next, SNT_NORMAL); } static inline void @@ -2801,11 +2830,13 @@ static inline void put_prev_set_next_task(struct rq *rq, __put_prev_set_next_dl_server(rq, prev, next); - if (next == prev) + if (next == prev) { + next->sched_class->set_next_task(rq, next, SNT_REPICK); return; + } prev->sched_class->put_prev_task(rq, prev, next); - next->sched_class->set_next_task(rq, next, true); + next->sched_class->set_next_task(rq, next, SNT_PICK); } /* @@ -3138,6 +3169,25 @@ static inline void attach_one_task(struct rq *rq, struct task_struct *p) attach_task(rq, p); } +/* + * __attach_tasks() - attaches a list of tasks (using se.group_node) to + * the new rq + */ +static inline void __attach_tasks(struct rq *rq, struct list_head *tasks) +{ + guard(rq_lock)(rq); + update_rq_clock(rq); + + while (!list_empty(tasks)) { + struct task_struct *p; + + p = list_first_entry(tasks, struct task_struct, se.group_node); + list_del_init(&p->se.group_node); + + attach_task(rq, p); + } +} + #ifdef CONFIG_PREEMPT_RT # define SCHED_NR_MIGRATE_BREAK 8 #else @@ -4252,4 +4302,10 @@ DEFINE_CLASS_IS_UNCONDITIONAL(sched_change) #include "ext/ext.h" +#ifdef CONFIG_PREFERRED_CPU +void sched_push_current_non_preferred_cpu(struct rq *rq); +#else /* !CONFIG_PREFERRED_CPU */ +static inline void sched_push_current_non_preferred_cpu(struct rq *rq) { } +#endif + #endif /* _KERNEL_SCHED_SCHED_H */ diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c index c909ca0d8c87..1e0109ec36b3 100644 --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -27,8 +27,11 @@ wakeup_preempt_stop(struct rq *rq, struct task_struct *p, int flags) /* we're never preempted */ } -static void set_next_task_stop(struct rq *rq, struct task_struct *stop, bool first) +static void set_next_task_stop(struct rq *rq, struct task_struct *stop, enum snt_e type) { + if (type == SNT_REPICK) + return; + stop->se.exec_start = rq_clock_task(rq); } diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 3dab0253976f..919d0fb00bd9 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -32,6 +32,20 @@ static int __init sched_debug_setup(char *str) } early_param("sched_verbose", sched_debug_setup); +#ifdef CONFIG_SCHED_SMT +static bool sched_smt_asym_packing __read_mostly; + +static int __init setup_sched_smt_asym_packing(char *str) +{ + if (strcmp(str, "on")) + return 0; + + sched_smt_asym_packing = true; + return 1; +} +__setup("sched_smt_asym_packing=", setup_sched_smt_asym_packing); +#endif + static inline bool sched_debug(void) { return sched_debug_verbose; @@ -1954,6 +1968,10 @@ sd_init(struct sched_domain_topology_level *tl, if (WARN_ONCE(sd_flags & ~TOPOLOGY_SD_FLAGS, "wrong sd_flags in topology description\n")) sd_flags &= TOPOLOGY_SD_FLAGS; +#ifdef CONFIG_SCHED_SMT + if (sched_smt_asym_packing && (sd_flags & SD_SHARE_CPUCAPACITY)) + sd_flags |= SD_ASYM_PACKING; +#endif sd_flags |= asym_cpu_capacity_classify(sd_span, cpu_map); *sd = (struct sched_domain){ diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index d033f600f48c..477e4bf9c01e 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -174,15 +174,11 @@ EXPORT_SYMBOL_GPL(__wake_up_locked_key); * @mode: which threads * @key: opaque value to be passed to wakeup targets * - * The sync wakeup differs that the waker knows that it will schedule - * away soon, so while the target thread will be woken up, it will not - * be migrated to another CPU - ie. the two threads are 'synchronized' - * with each other. This can prevent needless bouncing between CPUs. + * Passes WF_SYNC to waitqueue wake functions. The default wake function + * forwards it to the scheduler; see WF_SYNC for the hint's semantics. * - * On UP it can prevent extra preemption. - * - * If this function wakes up a task, it executes a full memory barrier before - * accessing the task state. + * If this function wakes up a task, it executes a full memory barrier + * before accessing the task state. */ void __wake_up_sync_key(struct wait_queue_head *wq_head, unsigned int mode, void *key) @@ -200,15 +196,7 @@ EXPORT_SYMBOL_GPL(__wake_up_sync_key); * @mode: which threads * @key: opaque value to be passed to wakeup targets * - * The sync wakeup differs in that the waker knows that it will schedule - * away soon, so while the target thread will be woken up, it will not - * be migrated to another CPU - ie. the two threads are 'synchronized' - * with each other. This can prevent needless bouncing between CPUs. - * - * On UP it can prevent extra preemption. - * - * If this function wakes up a task, it executes a full memory barrier before - * accessing the task state. + * Same as __wake_up_sync_key(), but called with @wq_head->lock held. */ void __wake_up_locked_sync_key(struct wait_queue_head *wq_head, unsigned int mode, void *key) diff --git a/kernel/smp.c b/kernel/smp.c index b696bcc60c08..8f530a094c30 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -87,6 +87,7 @@ int smpcfd_dead_cpu(unsigned int cpu) free_cpumask_var(cfd->cpumask); free_cpumask_var(cfd->cpumask_ipi); + irq_work_run_cpu(cpu); return 0; } diff --git a/kernel/smpboot.c b/kernel/smpboot.c index 4503b60ce9bd..3f60e8c6dd30 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -103,6 +103,7 @@ static int smpboot_thread_fn(void *data) { struct smpboot_thread_data *td = data; struct smp_hotplug_thread *ht = td->ht; + bool should_run; while (1) { set_current_state(TASK_INTERRUPTIBLE); @@ -117,7 +118,8 @@ static int smpboot_thread_fn(void *data) return 0; } - if (kthread_should_park()) { + should_run = td->status == HP_THREAD_ACTIVE && ht->thread_should_run(td->cpu); + if (kthread_should_park() && !should_run) { __set_current_state(TASK_RUNNING); preempt_enable(); if (ht->park && td->status == HP_THREAD_ACTIVE) { @@ -151,7 +153,7 @@ static int smpboot_thread_fn(void *data) continue; } - if (!ht->thread_should_run(td->cpu)) { + if (!should_run) { preempt_enable_no_resched(); schedule(); } else { diff --git a/lib/bitmap.c b/lib/bitmap.c index ed685127a107..d1cb8a507c60 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -308,6 +308,23 @@ bool __bitmap_intersects(const unsigned long *bitmap1, } EXPORT_SYMBOL(__bitmap_intersects); +bool __bitmap_intersects_and(const unsigned long *bitmap1, + const unsigned long *bitmap2, + const unsigned long *bitmap3, unsigned int bits) +{ + unsigned int k, lim = bits / BITS_PER_LONG; + + for (k = 0; k < lim; ++k) + if (bitmap1[k] & bitmap2[k] & bitmap3[k]) + return true; + + if (bits % BITS_PER_LONG) + if ((bitmap1[k] & bitmap2[k] & bitmap3[k]) & BITMAP_LAST_WORD_MASK(bits)) + return true; + return false; +} +EXPORT_SYMBOL(__bitmap_intersects_and); + bool __bitmap_subset(const unsigned long *bitmap1, const unsigned long *bitmap2, unsigned int bits) { diff --git a/tools/perf/trace/beauty/include/uapi/linux/sched.h b/tools/perf/trace/beauty/include/uapi/linux/sched.h index 33a4624285cd..19ffeba89428 100644 --- a/tools/perf/trace/beauty/include/uapi/linux/sched.h +++ b/tools/perf/trace/beauty/include/uapi/linux/sched.h @@ -53,7 +53,7 @@ */ #define UNSHARE_EMPTY_MNTNS 0x00100000 /* Unshare an empty mount namespace. */ -#ifndef __ASSEMBLY__ +#ifndef __ASSEMBLER__ /** * struct clone_args - arguments for the clone3 syscall * @flags: Flags for the new process as listed above. |
