From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
Hagar Hemdan <hagarhem@amazon.com>,
linux-kernel@vger.kernel.org, wuchi.zero@gmail.com
Subject: Re: [PATCH] /sched/core: Fix Unixbench spawn test regression
Date: Mon, 10 Mar 2025 16:29:10 +0100 [thread overview]
Message-ID: <8ddd7bb2-3a18-48b5-85c6-23263134308a@arm.com> (raw)
In-Reply-To: <CAKfTPtCfd_=gm7rsT_qBL8pw5uybEvYH4N2tvxpKndxxi4L7oA@mail.gmail.com>
On 10/03/2025 14:59, Vincent Guittot wrote:
> On Thu, 6 Mar 2025 at 17:26, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:
>>
>> Hagar reported a 30% drop in UnixBench spawn test with commit
>> eff6c8ce8d4d ("sched/core: Reduce cost of sched_move_task when config
>> autogroup") on a m6g.xlarge AWS EC2 instance with 4 vCPUs and 16 GiB RAM
>> (aarch64) (single level MC sched domain) [1].
>>
>> There is an early bail from sched_move_task() if p->sched_task_group is
>> equal to p's 'cpu cgroup' (sched_get_task_group()). E.g. both are
>> pointing to taskgroup '/user.slice/user-1000.slice/session-1.scope'
>> (Ubuntu '22.04.5 LTS').
>
> Isn't this same use case that has been used by commit eff6c8ce8d4d to
> show the benefit of adding the test if ((group ==
> tsk->sched_task_group) ?
> Adding Wuchi who added the condition
IMHO, UnixBench spawn reports a performance number according to how many
tasks could be spawned whereas, IIUC, commit eff6c8ce8d4d was reporting
the time spend in sched_move_task().
[...]
next prev parent reply other threads:[~2025-03-10 15:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-06 16:26 Dietmar Eggemann
2025-03-07 11:07 ` Hagar Hemdan
2025-03-10 13:59 ` Vincent Guittot
2025-03-10 15:29 ` Dietmar Eggemann [this message]
2025-03-11 16:35 ` Vincent Guittot
2025-03-12 14:41 ` Dietmar Eggemann
2025-03-12 16:35 ` Vincent Guittot
2025-03-13 9:21 ` Hagar Hemdan
2025-03-14 16:06 ` Vincent Guittot
2025-03-14 16:20 ` Hagar Hemdan
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