Messages in this thread | | | Date | Thu, 12 Dec 2019 16:04:29 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/fair: Optimize select_idle_cpu |
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On Thu, Dec 12, 2019 at 10:41:02PM +0800, Cheng Jian wrote: > select_idle_cpu will scan the LLC domain for idle CPUs, > it's always expensive. so commit > 1ad3aaf3fcd2 ("sched/core: Implement new approach to scale select_idle_cpu()") > introduces a way to limit how many CPUs we scan. > > But this also lead to the following issue: > > Our threads are all bind to the front CPUs of the LLC domain, > and now all the threads runs on the last CPU of them. nr is > always less than the cpumask_weight, for_each_cpu_wrap can't > find the CPU which our threads can run on, so the threads stay > at the last CPU all the time. > > Fixes: 1ad3aaf3fcd2 ("sched/core: Implement new approach to scale select_idle_cpu()") > Signed-off-by: Cheng Jian <cj.chengjian@huawei.com> > --- > kernel/sched/fair.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 08a233e97a01..16a29b570803 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5834,6 +5834,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t > s64 delta; > int this = smp_processor_id(); > int cpu, nr = INT_MAX, si_cpu = -1; > + struct cpumask cpus;
NAK, you must not put a cpumask on stack.
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