Messages in this thread | | | Date | Wed, 13 Jul 2022 11:47:08 +0800 | From | Chen Yu <> | Subject | Re: [PATCH 1/5] sched/fair: ignore SIS_UTIL when has idle core |
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On Tue, Jul 12, 2022 at 04:20:32PM +0800, Abel Wu wrote: > When SIS_UTIL is enabled, SIS domain scan will be skipped if > the LLC is overloaded. Since the overloaded status is checked > in the load balancing at LLC level, the interval is llc_size > miliseconds. The duration might be long enough to affect the > overall system throughput if idle cores are out of reach in > SIS domain scan. The idle core scan was skipped in SIS_UTIL because we saw better improvement in some benchmarks. But yes, we could make has_idle_core to scan anyway no matter what the system load is, if we have some data to support it. I'll test this patch on top of latest sched/core branch to see if this makes a difference.
thanks, Chenyu > > Signed-off-by: Abel Wu <wuyun.abel@bytedance.com> > --- > kernel/sched/fair.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index a78d2e3b9d49..cd758b3616bd 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6392,16 +6392,19 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool > struct sched_domain *this_sd; > u64 time = 0; > > - this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); > - if (!this_sd) > - return -1; > - > cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); > > - if (sched_feat(SIS_PROP) && !has_idle_core) { > + if (has_idle_core) > + goto scan; > + > + if (sched_feat(SIS_PROP)) { > u64 avg_cost, avg_idle, span_avg; > unsigned long now = jiffies; > > + this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); > + if (!this_sd) > + return -1; > + > /* > * If we're busy, the assumption that the last idle period > * predicts the future is flawed; age away the remaining > @@ -6436,7 +6439,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool > return -1; > } > } > - > +scan: > for_each_cpu_wrap(cpu, cpus, target + 1) { > if (has_idle_core) { > i = select_idle_core(p, cpu, cpus, &idle_cpu); > -- > 2.31.1 >
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