Messages in this thread Patch in this message | | | Subject | Re: oltp ~10% regression with 2.6.27-rc5 on stoakley machine | From | Peter Zijlstra <> | Date | Sat, 20 Sep 2008 23:38:02 +0200 |
| |
> > ------- Comment #4 from ming.m.lin@intel.com 2008-09-17 17:55 ------- > sched_switch trace of oltp in 2.6.27-rc4 > http://myfreefilehosting.com/f/fc6c8eaacf_1.31MB > > sched_switch trace of oltp in 2.6.27-rc5 > http://myfreefilehosting.com/f/a2f9aea1b0_0.42MB > > Compared the 2 trace files, you can find that (at most time), > with 2.6.27-rc5, mysql switches to sysbench when it's going to sleep > mysqld-3791 [07] 151.421836: 3791:120:R + 3803:120:S > mysqld-3791 [07] 151.421876: 3791:120:S ==> 3803:120:R > sysbench-3803 [07] 151.421878: 3803:120:R + 3791:120:S > sysbench-3803 [07] 151.421887: 3803:120:S ==> 3791:120:R > > with 2.6.27-rc4, mysql switches to sysbench when it's still running > mysqld-3674 [07] 95.960220: 3674:120:R + 3687:120:S > mysqld-3674 [07] 95.960220: 3674:120:R ==> 3687:120:R > sysbench-3687 [07] 95.960220: 3687:120:S ==> 3674:120:R > > So with 2.6.27-rc5, sysbench wakes up mysql and then switches to it (mysql is > in sleep state) > > With 2.6.27-rc4, sysbench switches to mysql, no need to wake up it (mysql is > still in running state)
Ming, how does this work for you?
--- Subject: sched: wakeup preempt when small overlap
Aggresively preempt a task if its avg overlap is very small, this should avoid the task going to sleep and find it still running when we schedule back to it - saving a wakeup.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- diff --git a/include/linux/sched.h b/include/linux/sched.h index 7b4592c..cb44774 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -897,7 +897,7 @@ struct sched_class { void (*yield_task) (struct rq *rq); int (*select_task_rq)(struct task_struct *p, int sync); - void (*check_preempt_curr) (struct rq *rq, struct task_struct *p); + void (*check_preempt_curr) (struct rq *rq, struct task_struct *p, int sync); struct task_struct * (*pick_next_task) (struct rq *rq); void (*put_prev_task) (struct rq *rq, struct task_struct *p); diff --git a/kernel/sched.c b/kernel/sched.c index 32d56d6..e17d506 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -609,9 +609,9 @@ struct rq { static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); -static inline void check_preempt_curr(struct rq *rq, struct task_struct *p) +static inline void check_preempt_curr(struct rq *rq, struct task_struct *p, int sync) { - rq->curr->sched_class->check_preempt_curr(rq, p); + rq->curr->sched_class->check_preempt_curr(rq, p, sync); } static inline int cpu_of(struct rq *rq) @@ -2299,7 +2299,7 @@ out_activate: out_running: trace_sched_wakeup(rq, p); - check_preempt_curr(rq, p); + check_preempt_curr(rq, p, sync); p->state = TASK_RUNNING; #ifdef CONFIG_SMP @@ -2432,7 +2432,7 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags) inc_nr_running(rq); } trace_sched_wakeup_new(rq, p); - check_preempt_curr(rq, p); + check_preempt_curr(rq, p, 0); #ifdef CONFIG_SMP if (p->sched_class->task_wake_up) p->sched_class->task_wake_up(rq, p); @@ -2889,7 +2889,7 @@ static void pull_task(struct rq *src_rq, struct task_struct *p, * Note that idle threads have a prio of MAX_PRIO, for this test * to be always true for them. */ - check_preempt_curr(this_rq, p); + check_preempt_curr(this_rq, p, 0); } /* @@ -6015,7 +6015,7 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) set_task_cpu(p, dest_cpu); if (on_rq) { activate_task(rq_dest, p, 0); - check_preempt_curr(rq_dest, p); + check_preempt_curr(rq_dest, p, 0); } done: ret = 1; diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index a10ac0b..82a907c 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1331,7 +1331,7 @@ static inline int depth_se(struct sched_entity *se) /* * Preempt the current task with a newly woken task if needed: */ -static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) +static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync) { struct task_struct *curr = rq->curr; struct cfs_rq *cfs_rq = task_cfs_rq(curr); @@ -1348,6 +1348,8 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) if (unlikely(se == pse)) return; + cfs_rq_of(pse)->next = pse; + /* * We can come here with TIF_NEED_RESCHED already set from new task * wake up path. @@ -1355,8 +1357,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) if (test_tsk_need_resched(curr)) return; - cfs_rq_of(pse)->next = pse; - /* * Batch tasks do not preempt (their preemption is driven by * the tick): @@ -1367,6 +1367,13 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) if (!sched_feat(WAKEUP_PREEMPT)) return; + if (sched_feat(WAKEUP_OVERLAP) && sync && + se->avg_overlap < sysctl_sched_migration_cost && + pse->avg_overlap < sysctl_sched_migration_cost) { + resched_task(curr); + return; + } + /* * preemption test can be made between sibling entities who are in the * same cfs_rq i.e who have a common parent. Walk up the hierarchy of @@ -1649,7 +1656,7 @@ static void prio_changed_fair(struct rq *rq, struct task_struct *p, if (p->prio > oldprio) resched_task(rq->curr); } else - check_preempt_curr(rq, p); + check_preempt_curr(rq, p, 0); } /* @@ -1666,7 +1673,7 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p, if (running) resched_task(rq->curr); else - check_preempt_curr(rq, p); + check_preempt_curr(rq, p, 0); } /* Account for a task changing its policy or group. diff --git a/kernel/sched_features.h b/kernel/sched_features.h index 9353ca7..bf027a7 100644 --- a/kernel/sched_features.h +++ b/kernel/sched_features.h @@ -11,3 +11,4 @@ SCHED_FEAT(ASYM_GRAN, 1) SCHED_FEAT(LB_BIAS, 1) SCHED_FEAT(LB_WAKEUP_UPDATE, 1) SCHED_FEAT(ASYM_EFF_LOAD, 1) +SCHED_FEAT(WAKEUP_OVERLAP, 1) diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c index 3a4f92d..dec4cca 100644 --- a/kernel/sched_idletask.c +++ b/kernel/sched_idletask.c @@ -14,7 +14,7 @@ static int select_task_rq_idle(struct task_struct *p, int sync) /* * Idle tasks are unconditionally rescheduled: */ -static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p) +static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int sync) { resched_task(rq->idle); } @@ -76,7 +76,7 @@ static void switched_to_idle(struct rq *rq, struct task_struct *p, if (running) resched_task(rq->curr); else - check_preempt_curr(rq, p); + check_preempt_curr(rq, p, 0); } static void prio_changed_idle(struct rq *rq, struct task_struct *p, @@ -93,7 +93,7 @@ static void prio_changed_idle(struct rq *rq, struct task_struct *p, if (p->prio > oldprio) resched_task(rq->curr); } else - check_preempt_curr(rq, p); + check_preempt_curr(rq, p, 0); } /* diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 04875ef..2e228bd 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -787,7 +787,7 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p) /* * Preempt the current task with a newly woken task if needed: */ -static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p) +static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int sync) { if (p->prio < rq->curr->prio) { resched_task(rq->curr);
| |