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| author | Peter Oskolkov <posk@google.com> | 2020-09-30 10:35:32 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-10-03 16:30:52 +0200 |
| commit | 9abb897345ce1d41257567f571a78137c961c405 (patch) | |
| tree | a5a00908bccdf1e192bc2da9a5280e666f8f9d8b /kernel/sched | |
| parent | f166b111e0491486fca0d105f09655ab718bd1c8 (diff) | |
| download | linux-stable-9abb897345ce1d41257567f571a78137c961c405.tar.gz linux-stable-9abb897345ce1d41257567f571a78137c961c405.tar.bz2 linux-stable-9abb897345ce1d41257567f571a78137c961c405.zip | |
sched/fair: Tweak pick_next_entity()
Currently, pick_next_entity(...) has the following structure
(simplified):
[...]
if (last_buddy_ok())
result = last_buddy;
if (next_buddy_ok())
result = next_buddy;
[...]
The intended behavior is to prefer next buddy over last buddy;
the current code somewhat obfuscates this, and also wastes
cycles checking the last buddy when eventually the next buddy is
picked up.
So this patch refactors two 'ifs' above into
[...]
if (next_buddy_ok())
result = next_buddy;
else if (last_buddy_ok())
result = last_buddy;
[...]
Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guitttot@linaro.org>
Link: https://lkml.kernel.org/r/20200930173532.1069092-1-posk@google.com
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/fair.c | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fc3410b8b990..cec6cf9b2bb3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4465,17 +4465,17 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) se = second; } - /* - * Prefer last buddy, try to return the CPU to a preempted task. - */ - 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) + if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) { + /* + * Someone really wants this to run. If it's not unfair, run it. + */ se = cfs_rq->next; + } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) { + /* + * Prefer last buddy, try to return the CPU to a preempted task. + */ + se = cfs_rq->last; + } clear_buddies(cfs_rq, se); |