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sched,fair: Alternative sched_slice()

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The current sched_slice() seems to have issues; there's two possible
things that could be improved:

 - the 'nr_running' used for __sched_period() is daft when cgroups are
   considered. Using the RQ wide h_nr_running seems like a much more
   consistent number.

 - (esp) cgroups can slice it real fine, which makes for easy
   over-scheduling, ensure min_gran is what the name says.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210412102001.611897312@infradead.org
This commit is contained in:
Peter Zijlstra 2021-03-25 13:44:46 +01:00
parent d27e9ae2f2
commit 0c2de3f054
2 changed files with 14 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

12
kernel/sched/fair.c
View file

@ -687,7 +687,13 @@ static u64 __sched_period(unsigned long nr_running)
*/
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
unsigned int nr_running = cfs_rq->nr_running;
u64 slice;
if (sched_feat(ALT_PERIOD))
nr_running = rq_of(cfs_rq)->cfs.h_nr_running;
slice = __sched_period(nr_running + !se->on_rq);
for_each_sched_entity(se) {
struct load_weight *load;
@ -704,6 +710,10 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
}
slice = __calc_delta(slice, se->load.weight, load);
}
if (sched_feat(BASE_SLICE))
slice = max(slice, (u64)sysctl_sched_min_granularity);
return slice;
}

3
kernel/sched/features.h
View file

@ -90,3 +90,6 @@ SCHED_FEAT(WA_BIAS, true)
*/
SCHED_FEAT(UTIL_EST, true)
SCHED_FEAT(UTIL_EST_FASTUP, true)
SCHED_FEAT(ALT_PERIOD, true)
SCHED_FEAT(BASE_SLICE, true)