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| author | Peter Zijlstra <peterz@infradead.org> | 2016-11-28 23:03:05 -0800 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2016-11-29 14:02:21 +0100 |
| commit | c1de45ca831acee9b72c9320dde447edafadb43f (patch) | |
| tree | bd4f7de61de5db4208a9701dfc3c5e9390665c12 /include/linux/sched.h | |
| parent | bb8313b603eb8fd52de48a079bfcd72dcab2ef1e (diff) | |
| download | lwn-c1de45ca831acee9b72c9320dde447edafadb43f.tar.gz lwn-c1de45ca831acee9b72c9320dde447edafadb43f.zip | |
sched/idle: Add support for tasks that inject idle
Idle injection drivers such as Intel powerclamp and ACPI PAD drivers use
realtime tasks to take control of CPU then inject idle. There are two
issues with this approach:
1. Low efficiency: injected idle task is treated as busy so sched ticks
do not stop during injected idle period, the result of these
unwanted wakeups can be ~20% loss in power savings.
2. Idle accounting: injected idle time is presented to user as busy.
This patch addresses the issues by introducing a new PF_IDLE flag which
allows any given task to be treated as idle task while the flag is set.
Therefore, idle injection tasks can run through the normal flow of NOHZ
idle enter/exit to get the correct accounting as well as tick stop when
possible.
The implication is that idle task is then no longer limited to PID == 0.
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'include/linux/sched.h')
| -rw-r--r-- | include/linux/sched.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 348f51b0ec92..114c7fcb6af6 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2254,6 +2254,7 @@ extern void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, /* * Per process flags */ +#define PF_IDLE 0x00000002 /* I am an IDLE thread */ #define PF_EXITING 0x00000004 /* getting shut down */ #define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */ #define PF_VCPU 0x00000010 /* I'm a virtual CPU */ @@ -2609,7 +2610,7 @@ extern struct task_struct *idle_task(int cpu); */ static inline bool is_idle_task(const struct task_struct *p) { - return p->pid == 0; + return !!(p->flags & PF_IDLE); } extern struct task_struct *curr_task(int cpu); extern void ia64_set_curr_task(int cpu, struct task_struct *p); |