Messages in this thread | | | Subject | Re: [PATCH] sched/fair: Optimize select_idle_cpu | From | "chengjian (D)" <> | Date | Fri, 13 Dec 2019 17:47:08 +0800 |
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On 2019/12/12 23:44, Valentin Schneider wrote: > On 12/12/2019 15:24, Peter Zijlstra wrote: >> On Thu, Dec 12, 2019 at 10:41:02PM +0800, Cheng Jian wrote: >> >>> Fixes: 1ad3aaf3fcd2 ("sched/core: Implement new approach to scale select_idle_cpu()") >> The 'funny' thing is that select_idle_core() actually does the right >> thing. >> >> Copying that should work: >> >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 08a233e97a01..416d574dcebf 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -5828,6 +5837,7 @@ static inline int select_idle_smt(struct task_struct *p, int target) >> */ >> static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target) >> { >> + struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); >> struct sched_domain *this_sd; >> u64 avg_cost, avg_idle; >> u64 time, cost; >> @@ -5859,11 +5869,11 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t >> >> time = cpu_clock(this); >> >> - for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { >> + cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); >> + >> + for_each_cpu_wrap(cpu, cpus, target) { >> if (!--nr) >> return si_cpu; >> - if (!cpumask_test_cpu(cpu, p->cpus_ptr)) >> - continue; >> if (available_idle_cpu(cpu)) >> break; >> if (si_cpu == -1 && sched_idle_cpu(cpu)) >> > That looks sane enough. I'd only argue the changelog should directly point > out that the issue is we consume some CPUs out of 'nr' that are not allowed > for the task and thus waste our attempts. > > .
Hi,Valentin
Yeah,Yours are more clear.
Thank you so much.
-- Cheng Jian
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