Messages in this thread | | | Subject | Re: [PATCH 1/2] nohz: Affine unpinned timers to housekeepers | From | Mike Galbraith <> | Date | Wed, 02 Sep 2015 11:38:09 +0200 |
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On Tue, 2015-09-01 at 22:47 +0200, Frederic Weisbecker wrote: > On Tue, Sep 01, 2015 at 07:14:13PM +0000, Jiang, Yunhong wrote: > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > > index 8b864ec..0902e4d 100644 > > > --- a/kernel/sched/core.c > > > +++ b/kernel/sched/core.c > > > @@ -623,18 +623,21 @@ int get_nohz_timer_target(void) > > > int i, cpu = smp_processor_id(); > > > struct sched_domain *sd; > > > > > > - if (!idle_cpu(cpu)) > > > + if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu)) > > > return cpu; > > > > > > rcu_read_lock(); > > > for_each_domain(cpu, sd) { > > > for_each_cpu(i, sched_domain_span(sd)) { > > > - if (!idle_cpu(i)) { > > > + if (!idle_cpu(i) && is_housekeeping_cpu(cpu)) { > > > > Hi, Frederic, sorry for a naive question. Per my understanding, the tick_nohz_full_mask is added to cpu_isolated_map in > > sched_init_smp(), and the cpu_isolated_map is excluded from sched_domain in init_sched_domains(), so why check here? > > Very good observation! But it's better to keep this check in the domain loop in > case things change in the future such as removing that cpu_isolated_map inclusion > or other suprises.
IMHO, nohz_full -> cpu_isolated_map removal really wants to happen. NO_HZ_FULL_ALL currently means "Woohoo, next stop NR_CPUS=0".
-Mike
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