From: Peter Zijlstra <peterz@infradead.org>
To: Barry Song <song.bao.hua@hisilicon.com>
Cc: vincent.guittot@linaro.org, mingo@redhat.com,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, valentin.schneider@arm.com,
juri.lelli@redhat.com, bristot@redhat.com,
linux-kernel@vger.kernel.org, guodong.xu@linaro.org,
yangyicong@huawei.com, tangchengchang@huawei.com,
linuxarm@huawei.com
Subject: Re: [PATCH] sched: fair: don't depend on wake_wide if waker and wakee are already in same LLC
Date: Wed, 26 May 2021 14:15:31 +0200 [thread overview]
Message-ID: <YK474+4xpYlAha+2@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210526091057.1800-1-song.bao.hua@hisilicon.com>
$subject is weird; sched/fair: is the right tag, and then start with a
capital letter.
On Wed, May 26, 2021 at 09:10:57PM +1200, Barry Song wrote:
> when waker and wakee are already in the same LLC, it is pointless to worry
> about the competition caused by pulling wakee to waker's LLC domain.
But there's more than LLC.
> Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
> ---
> kernel/sched/fair.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 3248e24a90b0..cfb1bd47acc3 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6795,7 +6795,15 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
> new_cpu = prev_cpu;
> }
>
> - want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
> + /*
> + * we use wake_wide to make smarter pull and avoid cruel
> + * competition because of jam-packed tasks in waker's LLC
> + * domain. But if waker and wakee have been already in
> + * same LLC domain, it seems it is pointless to depend
> + * on wake_wide
> + */
> + want_affine = (cpus_share_cache(cpu, prev_cpu) || !wake_wide(p)) &&
> + cpumask_test_cpu(cpu, p->cpus_ptr);
> }
And no supportive numbers...
next prev parent reply other threads:[~2021-05-26 12:16 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-26 9:10 [PATCH] sched: fair: don't depend on wake_wide if waker and wakee are already in same LLC Barry Song
2021-05-26 12:15 ` Peter Zijlstra [this message]
2021-05-26 21:38 ` Song Bao Hua (Barry Song)
2021-05-27 12:14 ` Mel Gorman
2021-05-31 22:21 ` Song Bao Hua (Barry Song)
2021-06-01 7:59 ` Mel Gorman
2021-06-01 8:09 ` Song Bao Hua (Barry Song)
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