Messages in this thread | | | From | Vincent Guittot <> | Date | Mon, 23 Aug 2021 12:09:32 +0200 | Subject | Re: [PATCH v3 4/4] sched: adjust sleeper credit for SCHED_IDLE entities |
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On Fri, 20 Aug 2021 at 03:04, Josh Don <joshdon@google.com> wrote: > > 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>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
> --- > 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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