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sched: Add new wakeup preemption mode: WAKEUP_RUNNING

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Create a new wakeup preemption mode, preempt towards tasks that run
shorter on avg. It sets next buddy to be sure we actually run the task
we preempted for.

Test results:

 root@twins:~# while :; do :; done &
 [1] 6537
 root@twins:~# while :; do :; done &
 [2] 6538
 root@twins:~# while :; do :; done &
 [3] 6539
 root@twins:~# while :; do :; done &
 [4] 6540

 root@twins:/home/peter# ./latt -c4 sleep 4
 Entries: 48 (clients=4)

 Averages:
 ------------------------------
        Max          4750 usec
        Avg           497 usec
        Stdev         737 usec

 root@twins:/home/peter# echo WAKEUP_RUNNING > /debug/sched_features

 root@twins:/home/peter# ./latt -c4 sleep 4
 Entries: 48 (clients=4)

 Averages:
 ------------------------------
        Max            14 usec
        Avg             5 usec
        Stdev           3 usec

Disabled by default - needs more testing.

Signed-off-by: Peter Zijlstra <[email protected]>
Acked-by: Mike Galbraith <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
LKML-Reference: <new-submission>
This commit is contained in:
Peter Zijlstra 2009-09-16 12:31:31 +02:00 • committed by Ingo Molnar
commit ad4b78bbcb
5 changed files with 29 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

17
kernel/sched.c
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@ -2458,6 +2458,7 @@ static void __sched_fork(struct task_struct *p)
p->se.avg_overlap = 0;
p->se.start_runtime = 0;
p->se.avg_wakeup = sysctl_sched_wakeup_granularity;
p->se.avg_running = 0;
#ifdef CONFIG_SCHEDSTATS
p->se.wait_start = 0;
@ -5310,14 +5311,13 @@ static inline void schedule_debug(struct task_struct *prev)
#endif
}
static void put_prev_task(struct rq *rq, struct task_struct *prev)
static void put_prev_task(struct rq *rq, struct task_struct *p)
{
if (prev->state == TASK_RUNNING) {
u64 runtime = prev->se.sum_exec_runtime;
u64 runtime = p->se.sum_exec_runtime - p->se.prev_sum_exec_runtime;
runtime -= prev->se.prev_sum_exec_runtime;
runtime = min_t(u64, runtime, 2*sysctl_sched_migration_cost);
update_avg(&p->se.avg_running, runtime);
if (p->state == TASK_RUNNING) {
/*
* In order to avoid avg_overlap growing stale when we are
* indeed overlapping and hence not getting put to sleep, grow
@ -5327,9 +5327,12 @@ static void put_prev_task(struct rq *rq, struct task_struct *prev)
* correlates to the amount of cache footprint a task can
* build up.
*/
update_avg(&prev->se.avg_overlap, runtime);
runtime = min_t(u64, runtime, 2*sysctl_sched_migration_cost);
update_avg(&p->se.avg_overlap, runtime);
} else {
update_avg(&p->se.avg_running, 0);
}
prev->sched_class->put_prev_task(rq, prev);
p->sched_class->put_prev_task(rq, p);
}
/*