From 4dd53d891ca46dcc1fde0376a33540d3fd83cb9a Mon Sep 17 00:00:00 2001 From: Venkatesh Pallipadi Date: Tue, 21 Dec 2010 17:09:00 -0800 Subject: softirqs: Free up pf flag PF_KSOFTIRQD Cleanup patch, freeing up PF_KSOFTIRQD and use per_cpu ksoftirqd pointer instead, as suggested by Eric Dumazet. Tested-by: Shaun Ruffell Signed-off-by: Venkatesh Pallipadi Signed-off-by: Peter Zijlstra LKML-Reference: <1292980144-28796-2-git-send-email-venki@google.com> Signed-off-by: Ingo Molnar --- include/linux/interrupt.h | 7 +++++++ include/linux/sched.h | 1 - 2 files changed, 7 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index 55e0d4253e49..a1382b9b5813 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -426,6 +426,13 @@ extern void raise_softirq(unsigned int nr); */ DECLARE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list); +DECLARE_PER_CPU(struct task_struct *, ksoftirqd); + +static inline struct task_struct *this_cpu_ksoftirqd(void) +{ + return this_cpu_read(ksoftirqd); +} + /* Try to send a softirq to a remote cpu. If this cannot be done, the * work will be queued to the local cpu. */ diff --git a/include/linux/sched.h b/include/linux/sched.h index d747f948b34e..af6e15fbfb78 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1715,7 +1715,6 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t * /* * Per process flags */ -#define PF_KSOFTIRQD 0x00000001 /* I am ksoftirqd */ #define PF_STARTING 0x00000002 /* being created */ #define PF_EXITING 0x00000004 /* getting shut down */ #define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */ -- cgit v1.2.3 From a1dabb6bfffccb897eff3e1d102dacf2a4bedf3b Mon Sep 17 00:00:00 2001 From: Venkatesh Pallipadi Date: Tue, 21 Dec 2010 17:09:01 -0800 Subject: time: Add nsecs_to_cputime64 interface for asm-generic Add nsecs_to_cputime64 interface. This is used in following patches that updates cpu irq stat based on ns granularity info in IRQ_TIME_ACCOUNTING. Tested-by: Shaun Ruffell Signed-off-by: Venkatesh Pallipadi Signed-off-by: Peter Zijlstra LKML-Reference: <1292980144-28796-3-git-send-email-venki@google.com> Signed-off-by: Ingo Molnar --- include/asm-generic/cputime.h | 3 +++ include/linux/jiffies.h | 1 + kernel/time.c | 23 +++++++++++++++++++++-- 3 files changed, 25 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/asm-generic/cputime.h b/include/asm-generic/cputime.h index 2bcc5c7c22a6..61e03dd7939e 100644 --- a/include/asm-generic/cputime.h +++ b/include/asm-generic/cputime.h @@ -30,6 +30,9 @@ typedef u64 cputime64_t; #define cputime64_to_jiffies64(__ct) (__ct) #define jiffies64_to_cputime64(__jif) (__jif) #define cputime_to_cputime64(__ct) ((u64) __ct) +#define cputime64_gt(__a, __b) ((__a) > (__b)) + +#define nsecs_to_cputime64(__ct) nsecs_to_jiffies64(__ct) /* diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index 6811f4bfc6e7..922aa313c9f9 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -307,6 +307,7 @@ extern clock_t jiffies_to_clock_t(long x); extern unsigned long clock_t_to_jiffies(unsigned long x); extern u64 jiffies_64_to_clock_t(u64 x); extern u64 nsec_to_clock_t(u64 x); +extern u64 nsecs_to_jiffies64(u64 n); extern unsigned long nsecs_to_jiffies(u64 n); #define TIMESTAMP_SIZE 30 diff --git a/kernel/time.c b/kernel/time.c index 32174359576f..55337a816b20 100644 --- a/kernel/time.c +++ b/kernel/time.c @@ -645,7 +645,7 @@ u64 nsec_to_clock_t(u64 x) } /** - * nsecs_to_jiffies - Convert nsecs in u64 to jiffies + * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64 * * @n: nsecs in u64 * @@ -657,7 +657,7 @@ u64 nsec_to_clock_t(u64 x) * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years */ -unsigned long nsecs_to_jiffies(u64 n) +u64 nsecs_to_jiffies64(u64 n) { #if (NSEC_PER_SEC % HZ) == 0 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */ @@ -674,6 +674,25 @@ unsigned long nsecs_to_jiffies(u64 n) #endif } + +/** + * nsecs_to_jiffies - Convert nsecs in u64 to jiffies + * + * @n: nsecs in u64 + * + * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. + * And this doesn't return MAX_JIFFY_OFFSET since this function is designed + * for scheduler, not for use in device drivers to calculate timeout value. + * + * note: + * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) + * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years + */ +unsigned long nsecs_to_jiffies(u64 n) +{ + return (unsigned long)nsecs_to_jiffies64(n); +} + #if (BITS_PER_LONG < 64) u64 get_jiffies_64(void) { -- cgit v1.2.3 From da7a735e51f9622eb3e1672594d4a41da01d7e4f Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 17 Jan 2011 17:03:27 +0100 Subject: sched: Fix switch_from_fair() When a task is taken out of the fair class we must ensure the vruntime is properly normalized because when we put it back in it will assume to be normalized. The case that goes wrong is when changing away from the fair class while sleeping. Sleeping tasks have non-normalized vruntime in order to make sleeper-fairness work. So treat the switch away from fair as a wakeup and preserve the relative vruntime. Also update sysrq-n to call the ->switch_{to,from} methods. Reported-by: Onkalo Samu Signed-off-by: Peter Zijlstra LKML-Reference: Signed-off-by: Ingo Molnar --- include/linux/sched.h | 8 +++----- kernel/sched.c | 25 ++++++++++++++----------- kernel/sched_fair.c | 42 ++++++++++++++++++++++++++++++++++++------ kernel/sched_idletask.c | 7 +++---- kernel/sched_rt.c | 19 ++++++++++--------- kernel/sched_stoptask.c | 7 +++---- 6 files changed, 69 insertions(+), 39 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index af6e15fbfb78..0542774914d4 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1084,12 +1084,10 @@ struct sched_class { void (*task_tick) (struct rq *rq, struct task_struct *p, int queued); void (*task_fork) (struct task_struct *p); - void (*switched_from) (struct rq *this_rq, struct task_struct *task, - int running); - void (*switched_to) (struct rq *this_rq, struct task_struct *task, - int running); + void (*switched_from) (struct rq *this_rq, struct task_struct *task); + void (*switched_to) (struct rq *this_rq, struct task_struct *task); void (*prio_changed) (struct rq *this_rq, struct task_struct *task, - int oldprio, int running); + int oldprio); unsigned int (*get_rr_interval) (struct rq *rq, struct task_struct *task); diff --git a/kernel/sched.c b/kernel/sched.c index 8b718b59b09f..78fa75394011 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2057,14 +2057,14 @@ inline int task_curr(const struct task_struct *p) static inline void check_class_changed(struct rq *rq, struct task_struct *p, const struct sched_class *prev_class, - int oldprio, int running) + int oldprio) { if (prev_class != p->sched_class) { if (prev_class->switched_from) - prev_class->switched_from(rq, p, running); - p->sched_class->switched_to(rq, p, running); - } else - p->sched_class->prio_changed(rq, p, oldprio, running); + prev_class->switched_from(rq, p); + p->sched_class->switched_to(rq, p); + } else if (oldprio != p->prio) + p->sched_class->prio_changed(rq, p, oldprio); } static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) @@ -2598,6 +2598,7 @@ static void __sched_fork(struct task_struct *p) p->se.sum_exec_runtime = 0; p->se.prev_sum_exec_runtime = 0; p->se.nr_migrations = 0; + p->se.vruntime = 0; #ifdef CONFIG_SCHEDSTATS memset(&p->se.statistics, 0, sizeof(p->se.statistics)); @@ -4696,11 +4697,10 @@ void rt_mutex_setprio(struct task_struct *p, int prio) if (running) p->sched_class->set_curr_task(rq); - if (on_rq) { + if (on_rq) enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0); - check_class_changed(rq, p, prev_class, oldprio, running); - } + check_class_changed(rq, p, prev_class, oldprio); task_rq_unlock(rq, &flags); } @@ -5028,11 +5028,10 @@ recheck: if (running) p->sched_class->set_curr_task(rq); - if (on_rq) { + if (on_rq) activate_task(rq, p, 0); - check_class_changed(rq, p, prev_class, oldprio, running); - } + check_class_changed(rq, p, prev_class, oldprio); __task_rq_unlock(rq); raw_spin_unlock_irqrestore(&p->pi_lock, flags); @@ -8237,6 +8236,8 @@ EXPORT_SYMBOL(__might_sleep); #ifdef CONFIG_MAGIC_SYSRQ static void normalize_task(struct rq *rq, struct task_struct *p) { + const struct sched_class *prev_class = p->sched_class; + int old_prio = p->prio; int on_rq; on_rq = p->se.on_rq; @@ -8247,6 +8248,8 @@ static void normalize_task(struct rq *rq, struct task_struct *p) activate_task(rq, p, 0); resched_task(rq->curr); } + + check_class_changed(rq, p, prev_class, old_prio); } void normalize_rt_tasks(void) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 4cbc9121094c..55040f3938d8 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -4078,33 +4078,62 @@ static void task_fork_fair(struct task_struct *p) * Priority of the task has changed. Check to see if we preempt * the current task. */ -static void prio_changed_fair(struct rq *rq, struct task_struct *p, - int oldprio, int running) +static void +prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) { + if (!p->se.on_rq) + return; + /* * Reschedule if we are currently running on this runqueue and * our priority decreased, or if we are not currently running on * this runqueue and our priority is higher than the current's */ - if (running) { + if (rq->curr == p) { if (p->prio > oldprio) resched_task(rq->curr); } else check_preempt_curr(rq, p, 0); } +static void switched_from_fair(struct rq *rq, struct task_struct *p) +{ + struct sched_entity *se = &p->se; + struct cfs_rq *cfs_rq = cfs_rq_of(se); + + /* + * Ensure the task's vruntime is normalized, so that when its + * switched back to the fair class the enqueue_entity(.flags=0) will + * do the right thing. + * + * If it was on_rq, then the dequeue_entity(.flags=0) will already + * have normalized the vruntime, if it was !on_rq, then only when + * the task is sleeping will it still have non-normalized vruntime. + */ + if (!se->on_rq && p->state != TASK_RUNNING) { + /* + * Fix up our vruntime so that the current sleep doesn't + * cause 'unlimited' sleep bonus. + */ + place_entity(cfs_rq, se, 0); + se->vruntime -= cfs_rq->min_vruntime; + } +} + /* * We switched to the sched_fair class. */ -static void switched_to_fair(struct rq *rq, struct task_struct *p, - int running) +static void switched_to_fair(struct rq *rq, struct task_struct *p) { + if (!p->se.on_rq) + return; + /* * We were most likely switched from sched_rt, so * kick off the schedule if running, otherwise just see * if we can still preempt the current task. */ - if (running) + if (rq->curr == p) resched_task(rq->curr); else check_preempt_curr(rq, p, 0); @@ -4190,6 +4219,7 @@ static const struct sched_class fair_sched_class = { .task_fork = task_fork_fair, .prio_changed = prio_changed_fair, + .switched_from = switched_from_fair, .switched_to = switched_to_fair, .get_rr_interval = get_rr_interval_fair, diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c index 41eb62a0808b..c82f26c1b7c3 100644 --- a/kernel/sched_idletask.c +++ b/kernel/sched_idletask.c @@ -52,14 +52,13 @@ static void set_curr_task_idle(struct rq *rq) { } -static void -switched_to_idle(struct rq *rq, struct task_struct *p, int running) +static void switched_to_idle(struct rq *rq, struct task_struct *p) { BUG(); } -static void prio_changed_idle(struct rq *rq, struct task_struct *p, - int oldprio, int running) +static void +prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio) { BUG(); } diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index c914ec747ca6..c381fdc18c64 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -1595,8 +1595,7 @@ static void rq_offline_rt(struct rq *rq) * When switch from the rt queue, we bring ourselves to a position * that we might want to pull RT tasks from other runqueues. */ -static void switched_from_rt(struct rq *rq, struct task_struct *p, - int running) +static void switched_from_rt(struct rq *rq, struct task_struct *p) { /* * If there are other RT tasks then we will reschedule @@ -1605,7 +1604,7 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p, * we may need to handle the pulling of RT tasks * now. */ - if (!rq->rt.rt_nr_running) + if (p->se.on_rq && !rq->rt.rt_nr_running) pull_rt_task(rq); } @@ -1624,8 +1623,7 @@ static inline void init_sched_rt_class(void) * with RT tasks. In this case we try to push them off to * other runqueues. */ -static void switched_to_rt(struct rq *rq, struct task_struct *p, - int running) +static void switched_to_rt(struct rq *rq, struct task_struct *p) { int check_resched = 1; @@ -1636,7 +1634,7 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p, * If that current running task is also an RT task * then see if we can move to another run queue. */ - if (!running) { + if (p->se.on_rq && rq->curr != p) { #ifdef CONFIG_SMP if (rq->rt.overloaded && push_rt_task(rq) && /* Don't resched if we changed runqueues */ @@ -1652,10 +1650,13 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p, * Priority of the task has changed. This may cause * us to initiate a push or pull. */ -static void prio_changed_rt(struct rq *rq, struct task_struct *p, - int oldprio, int running) +static void +prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio) { - if (running) { + if (!p->se.on_rq) + return; + + if (rq->curr == p) { #ifdef CONFIG_SMP /* * If our priority decreases while running, we diff --git a/kernel/sched_stoptask.c b/kernel/sched_stoptask.c index 2bf6b47058c1..84ec9bcf82d9 100644 --- a/kernel/sched_stoptask.c +++ b/kernel/sched_stoptask.c @@ -59,14 +59,13 @@ static void set_curr_task_stop(struct rq *rq) { } -static void switched_to_stop(struct rq *rq, struct task_struct *p, - int running) +static void switched_to_stop(struct rq *rq, struct task_struct *p) { BUG(); /* its impossible to change to this class */ } -static void prio_changed_stop(struct rq *rq, struct task_struct *p, - int oldprio, int running) +static void +prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio) { BUG(); /* how!?, what priority? */ } -- cgit v1.2.3 From ac53db596cc08ecb8040cfb6f71ae40c6f2041c4 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Tue, 1 Feb 2011 09:51:03 -0500 Subject: sched: Use a buddy to implement yield_task_fair() Use the buddy mechanism to implement yield_task_fair. This allows us to skip onto the next highest priority se at every level in the CFS tree, unless doing so would introduce gross unfairness in CPU time distribution. We order the buddy selection in pick_next_entity to check yield first, then last, then next. We need next to be able to override yield, because it is possible for the "next" and "yield" task to be different processen in the same sub-tree of the CFS tree. When they are, we need to go into that sub-tree regardless of the "yield" hint, and pick the correct entity once we get to the right level. Signed-off-by: Rik van Riel Signed-off-by: Peter Zijlstra LKML-Reference: <20110201095103.3a79e92a@annuminas.surriel.com> Signed-off-by: Ingo Molnar --- include/linux/sched.h | 2 - kernel/sched.c | 2 +- kernel/sched_debug.c | 2 +- kernel/sched_fair.c | 148 ++++++++++++++++++++++++++++++-------------------- kernel/sysctl.c | 7 --- 5 files changed, 90 insertions(+), 71 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index 0542774914d4..4e9fad271c30 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1942,8 +1942,6 @@ int sched_rt_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos); -extern unsigned int sysctl_sched_compat_yield; - #ifdef CONFIG_SCHED_AUTOGROUP extern unsigned int sysctl_sched_autogroup_enabled; diff --git a/kernel/sched.c b/kernel/sched.c index 477e1bcc63f9..ae5e1a19b9d6 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -324,7 +324,7 @@ struct cfs_rq { * 'curr' points to currently running entity on this cfs_rq. * It is set to NULL otherwise (i.e when none are currently running). */ - struct sched_entity *curr, *next, *last; + struct sched_entity *curr, *next, *last, *skip; unsigned int nr_spread_over; diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c index eb6cb8edd075..7bacd83a4158 100644 --- a/kernel/sched_debug.c +++ b/kernel/sched_debug.c @@ -179,7 +179,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) raw_spin_lock_irqsave(&rq->lock, flags); if (cfs_rq->rb_leftmost) - MIN_vruntime = (__pick_next_entity(cfs_rq))->vruntime; + MIN_vruntime = (__pick_first_entity(cfs_rq))->vruntime; last = __pick_last_entity(cfs_rq); if (last) max_vruntime = last->vruntime; diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index a785e08202cf..c0fbeb992833 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -68,14 +68,6 @@ static unsigned int sched_nr_latency = 8; */ unsigned int sysctl_sched_child_runs_first __read_mostly; -/* - * sys_sched_yield() compat mode - * - * This option switches the agressive yield implementation of the - * old scheduler back on. - */ -unsigned int __read_mostly sysctl_sched_compat_yield; - /* * SCHED_OTHER wake-up granularity. * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) @@ -419,7 +411,7 @@ static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) rb_erase(&se->run_node, &cfs_rq->tasks_timeline); } -static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq) +static struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) { struct rb_node *left = cfs_rq->rb_leftmost; @@ -429,6 +421,17 @@ static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq) return rb_entry(left, struct sched_entity, run_node); } +static struct sched_entity *__pick_next_entity(struct sched_entity *se) +{ + struct rb_node *next = rb_next(&se->run_node); + + if (!next) + return NULL; + + return rb_entry(next, struct sched_entity, run_node); +} + +#ifdef CONFIG_SCHED_DEBUG static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) { struct rb_node *last = rb_last(&cfs_rq->tasks_timeline); @@ -443,7 +446,6 @@ static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) * Scheduling class statistics methods: */ -#ifdef CONFIG_SCHED_DEBUG int sched_proc_update_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) @@ -1017,6 +1019,17 @@ static void __clear_buddies_next(struct sched_entity *se) } } +static void __clear_buddies_skip(struct sched_entity *se) +{ + for_each_sched_entity(se) { + struct cfs_rq *cfs_rq = cfs_rq_of(se); + if (cfs_rq->skip == se) + cfs_rq->skip = NULL; + else + break; + } +} + static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) { if (cfs_rq->last == se) @@ -1024,6 +1037,9 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) if (cfs_rq->next == se) __clear_buddies_next(se); + + if (cfs_rq->skip == se) + __clear_buddies_skip(se); } static void @@ -1099,7 +1115,7 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) return; if (cfs_rq->nr_running > 1) { - struct sched_entity *se = __pick_next_entity(cfs_rq); + struct sched_entity *se = __pick_first_entity(cfs_rq); s64 delta = curr->vruntime - se->vruntime; if (delta < 0) @@ -1143,13 +1159,27 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) static int wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); +/* + * Pick the next process, keeping these things in mind, in this order: + * 1) keep things fair between processes/task groups + * 2) pick the "next" process, since someone really wants that to run + * 3) pick the "last" process, for cache locality + * 4) do not run the "skip" process, if something else is available + */ static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq) { - struct sched_entity *se = __pick_next_entity(cfs_rq); + struct sched_entity *se = __pick_first_entity(cfs_rq); struct sched_entity *left = se; - if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) - se = cfs_rq->next; + /* + * Avoid running the skip buddy, if running something else can + * be done without getting too unfair. + */ + if (cfs_rq->skip == se) { + struct sched_entity *second = __pick_next_entity(se); + if (second && wakeup_preempt_entity(second, left) < 1) + se = second; + } /* * Prefer last buddy, try to return the CPU to a preempted task. @@ -1157,6 +1187,12 @@ static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq) if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) se = cfs_rq->last; + /* + * Someone really wants this to run. If it's not unfair, run it. + */ + if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) + se = cfs_rq->next; + clear_buddies(cfs_rq, se); return se; @@ -1333,52 +1369,6 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) hrtick_update(rq); } -/* - * sched_yield() support is very simple - we dequeue and enqueue. - * - * If compat_yield is turned on then we requeue to the end of the tree. - */ -static void yield_task_fair(struct rq *rq) -{ - struct task_struct *curr = rq->curr; - struct cfs_rq *cfs_rq = task_cfs_rq(curr); - struct sched_entity *rightmost, *se = &curr->se; - - /* - * Are we the only task in the tree? - */ - if (unlikely(rq->nr_running == 1)) - return; - - clear_buddies(cfs_rq, se); - - if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) { - update_rq_clock(rq); - /* - * Update run-time statistics of the 'current'. - */ - update_curr(cfs_rq); - - return; - } - /* - * Find the rightmost entry in the rbtree: - */ - rightmost = __pick_last_entity(cfs_rq); - /* - * Already in the rightmost position? - */ - if (unlikely(!rightmost || entity_before(rightmost, se))) - return; - - /* - * Minimally necessary key value to be last in the tree: - * Upon rescheduling, sched_class::put_prev_task() will place - * 'current' within the tree based on its new key value. - */ - se->vruntime = rightmost->vruntime + 1; -} - #ifdef CONFIG_SMP static void task_waking_fair(struct rq *rq, struct task_struct *p) @@ -1849,6 +1839,14 @@ static void set_next_buddy(struct sched_entity *se) } } +static void set_skip_buddy(struct sched_entity *se) +{ + if (likely(task_of(se)->policy != SCHED_IDLE)) { + for_each_sched_entity(se) + cfs_rq_of(se)->skip = se; + } +} + /* * Preempt the current task with a newly woken task if needed: */ @@ -1947,6 +1945,36 @@ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) } } +/* + * sched_yield() is very simple + * + * The magic of dealing with the ->skip buddy is in pick_next_entity. + */ +static void yield_task_fair(struct rq *rq) +{ + struct task_struct *curr = rq->curr; + struct cfs_rq *cfs_rq = task_cfs_rq(curr); + struct sched_entity *se = &curr->se; + + /* + * Are we the only task in the tree? + */ + if (unlikely(rq->nr_running == 1)) + return; + + clear_buddies(cfs_rq, se); + + if (curr->policy != SCHED_BATCH) { + update_rq_clock(rq); + /* + * Update run-time statistics of the 'current'. + */ + update_curr(cfs_rq); + } + + set_skip_buddy(se); +} + #ifdef CONFIG_SMP /************************************************** * Fair scheduling class load-balancing methods: diff --git a/kernel/sysctl.c b/kernel/sysctl.c index bc86bb32e126..cbfda7e2416e 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -360,13 +360,6 @@ static struct ctl_table kern_table[] = { .mode = 0644, .proc_handler = sched_rt_handler, }, - { - .procname = "sched_compat_yield", - .data = &sysctl_sched_compat_yield, - .maxlen = sizeof(unsigned int), - .mode = 0644, - .proc_handler = proc_dointvec, - }, #ifdef CONFIG_SCHED_AUTOGROUP { .procname = "sched_autogroup_enabled", -- cgit v1.2.3 From d95f412200652694e63e64bfd49f0ae274a54479 Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Tue, 1 Feb 2011 09:50:51 -0500 Subject: sched: Add yield_to(task, preempt) functionality Currently only implemented for fair class tasks. Add a yield_to_task method() to the fair scheduling class. allowing the caller of yield_to() to accelerate another thread in it's thread group, task group. Implemented via a scheduler hint, using cfs_rq->next to encourage the target being selected. We can rely on pick_next_entity to keep things fair, so noone can accelerate a thread that has already used its fair share of CPU time. This also means callers should only call yield_to when they really mean it. Calling it too often can result in the scheduler just ignoring the hint. Signed-off-by: Rik van Riel Signed-off-by: Marcelo Tosatti Signed-off-by: Mike Galbraith Signed-off-by: Peter Zijlstra LKML-Reference: <20110201095051.4ddb7738@annuminas.surriel.com> Signed-off-by: Ingo Molnar --- include/linux/sched.h | 2 ++ kernel/sched.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++ kernel/sched_fair.c | 20 ++++++++++++ 3 files changed, 107 insertions(+) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index 4e9fad271c30..c88b3bfbd09e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1058,6 +1058,7 @@ struct sched_class { void (*enqueue_task) (struct rq *rq, struct task_struct *p, int flags); void (*dequeue_task) (struct rq *rq, struct task_struct *p, int flags); void (*yield_task) (struct rq *rq); + bool (*yield_to_task) (struct rq *rq, struct task_struct *p, bool preempt); void (*check_preempt_curr) (struct rq *rq, struct task_struct *p, int flags); @@ -1972,6 +1973,7 @@ static inline int rt_mutex_getprio(struct task_struct *p) # define rt_mutex_adjust_pi(p) do { } while (0) #endif +extern bool yield_to(struct task_struct *p, bool preempt); extern void set_user_nice(struct task_struct *p, long nice); extern int task_prio(const struct task_struct *p); extern int task_nice(const struct task_struct *p); diff --git a/kernel/sched.c b/kernel/sched.c index ae5e1a19b9d6..2effcb71a478 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1686,6 +1686,39 @@ static void double_rq_unlock(struct rq *rq1, struct rq *rq2) __release(rq2->lock); } +#else /* CONFIG_SMP */ + +/* + * double_rq_lock - safely lock two runqueues + * + * Note this does not disable interrupts like task_rq_lock, + * you need to do so manually before calling. + */ +static void double_rq_lock(struct rq *rq1, struct rq *rq2) + __acquires(rq1->lock) + __acquires(rq2->lock) +{ + BUG_ON(!irqs_disabled()); + BUG_ON(rq1 != rq2); + raw_spin_lock(&rq1->lock); + __acquire(rq2->lock); /* Fake it out ;) */ +} + +/* + * double_rq_unlock - safely unlock two runqueues + * + * Note this does not restore interrupts like task_rq_unlock, + * you need to do so manually after calling. + */ +static void double_rq_unlock(struct rq *rq1, struct rq *rq2) + __releases(rq1->lock) + __releases(rq2->lock) +{ + BUG_ON(rq1 != rq2); + raw_spin_unlock(&rq1->lock); + __release(rq2->lock); +} + #endif static void calc_load_account_idle(struct rq *this_rq); @@ -5448,6 +5481,58 @@ void __sched yield(void) } EXPORT_SYMBOL(yield); +/** + * yield_to - yield the current processor to another thread in + * your thread group, or accelerate that thread toward the + * processor it's on. + * + * It's the caller's job to ensure that the target task struct + * can't go away on us before we can do any checks. + * + * Returns true if we indeed boosted the target task. + */ +bool __sched yield_to(struct task_struct *p, bool preempt) +{ + struct task_struct *curr = current; + struct rq *rq, *p_rq; + unsigned long flags; + bool yielded = 0; + + local_irq_save(flags); + rq = this_rq(); + +again: + p_rq = task_rq(p); + double_rq_lock(rq, p_rq); + while (task_rq(p) != p_rq) { + double_rq_unlock(rq, p_rq); + goto again; + } + + if (!curr->sched_class->yield_to_task) + goto out; + + if (curr->sched_class != p->sched_class) + goto out; + + if (task_running(p_rq, p) || p->state) + goto out; + + yielded = curr->sched_class->yield_to_task(rq, p, preempt); + if (yielded) + schedstat_inc(rq, yld_count); + +out: + double_rq_unlock(rq, p_rq); + local_irq_restore(flags); + + if (yielded) + schedule(); + + return yielded; +} +EXPORT_SYMBOL_GPL(yield_to); + /* * This task is about to go to sleep on IO. Increment rq->nr_iowait so * that process accounting knows that this is a task in IO wait state. diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index c0fbeb992833..027024694043 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1975,6 +1975,25 @@ static void yield_task_fair(struct rq *rq) set_skip_buddy(se); } +static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) +{ + struct sched_entity *se = &p->se; + + if (!se->on_rq) + return false; + + /* Tell the scheduler that we'd really like pse to run next. */ + set_next_buddy(se); + + /* Make p's CPU reschedule; pick_next_entity takes care of fairness. */ + if (preempt) + resched_task(rq->curr); + + yield_task_fair(rq); + + return true; +} + #ifdef CONFIG_SMP /************************************************** * Fair scheduling class load-balancing methods: @@ -4243,6 +4262,7 @@ static const struct sched_class fair_sched_class = { .enqueue_task = enqueue_task_fair, .dequeue_task = dequeue_task_fair, .yield_task = yield_task_fair, + .yield_to_task = yield_to_task_fair, .check_preempt_curr = check_preempt_wakeup, -- cgit v1.2.3