Messages in this thread Patch in this message | | | Date | Thu, 19 Aug 2021 18:04:03 -0700 | Subject | [PATCH v3 4/4] sched: adjust sleeper credit for SCHED_IDLE entities | From | Josh Don <> |
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Give reduced sleeper credit to SCHED_IDLE entities. As a result, woken SCHED_IDLE entities will take longer to preempt normal entities.
The benefit of this change is to make it less likely that a newly woken SCHED_IDLE entity will preempt a short-running normal entity before it blocks.
We still give a small sleeper credit to SCHED_IDLE entities, so that idle<->idle competition retains some fairness.
Example: With HZ=1000, spawned four threads affined to one cpu, one of which was set to SCHED_IDLE. Without this patch, wakeup latency for the SCHED_IDLE thread was ~1-2ms, with the patch the wakeup latency was ~5ms.
Signed-off-by: Josh Don <joshdon@google.com> --- kernel/sched/fair.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 31f40aa005b9..aa9c046d2aab 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4230,7 +4230,12 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) /* sleeps up to a single latency don't count. */ if (!initial) { - unsigned long thresh = sysctl_sched_latency; + unsigned long thresh; + + if (se_is_idle(se)) + thresh = sysctl_sched_min_granularity; + else + thresh = sysctl_sched_latency; /* * Halve their sleep time's effect, to allow -- 2.33.0.rc2.250.ged5fa647cd-goog
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