From: Bernd Schubert <bernd@bsbernd.com>
To: Bernd Schubert <bschubert@ddn.com>,
Joanne Koong <joannelkoong@gmail.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
Luis Henriques <luis@igalia.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2] fuse: Wake requests on the same cpu
Date: Mon, 20 Oct 2025 00:22:22 +0200 [thread overview]
Message-ID: <005ede4e-7e9f-454e-9360-ef04111ece29@bsbernd.com> (raw)
In-Reply-To: <b0717e48-0879-4af8-bd31-11a239dea787@bsbernd.com>
On 10/19/25 20:15, Bernd Schubert wrote:
>
>
> On 10/16/25 23:53, Bernd Schubert wrote:
>> On 10/16/25 22:13, Joanne Koong wrote:
>> And then
>>
>> bschubert2@imesrv3 ~>fio --directory=/tmp/dest --name=iops.\$jobnum --rw=randread --bs=4k --size=1G --numjobs=1 --iodepth=1 --time_based --runtime=30s --group_reporting --ioengine=psync --direct=1
>>
>>
>> With WF_CURRENT_CPU: READ: bw=269MiB/s
>> With WF_SYNC: READ: bw=214MiB/s
>> With plain wake_up: READ: bw=217MiB/s
>>
>
> The culprit with plain wake might be here
>
> fio-7669 [011] d..2. 13916.272607: sched_switch: prev_comm=fio prev_pid=7669 prev_prio=120 prev_state=S ==> next_comm=swapper/11 next_pid=
> ...
> <idle>-0 [011] d.s4. 13916.281747: sched_waking: comm=kworker/11:1 pid=297 prio=120 target_cpu=011
> <idle>-0 [011] d.s4. 13916.281749: sched_waking_extended: comm=kworker/11:1 pid=297 prio=120 prev_cpu=011 current_cpu=011 target_cpu=011
> <idle>-0 [011] dNs5. 13916.281769: sched_wakeup: comm=kworker/11:1 pid=297 prio=120 target_cpu=011
> <idle>-0 [011] dNs5. 13916.281769: sched_wakeup_extended: comm=kworker/11:1 pid=297 prio=120 prev_cpu=011 current_cpu=011 target_cpu=011
> <idle>-0 [011] d..2. 13916.281779: sched_switch: prev_comm=swapper/11 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/11:1 nex
> t_pid=297 next_prio=120
> kworker/11:1-297 [011] d.h3. 13916.282654: sched_waking: comm=fio pid=7669 prio=120 target_cpu=011
> kworker/11:1-297 [011] d.h3. 13916.282654: sched_waking_extended: comm=fio pid=7669 prio=120 prev_cpu=011 current_cpu=011 target_cpu=011
> kworker/11:1-297 [011] d.h3. 13916.282654: select_task_rq_fair <-select_task_rq
> kworker/11:1-297 [011] d.h3. 13916.282655: sched_migrate_task: comm=fio pid=7669 prio=120 orig_cpu=11 dest_cpu=26
>
>
> ==> migration from cpu=11 to cpu=26
>
> kworker/11:1-297 [011] d.h3. 13916.282657: sched_wake_idle_without_ipi: cpu=26
> <idle>-0 [026] dN.2. 13916.282686: sched_wakeup: comm=fio pid=7669 prio=120 target_cpu=026
> <idle>-0 [026] dN.2. 13916.282687: sched_wakeup_extended: comm=fio pid=7669 prio=120 prev_cpu=026 current_cpu=026 target_cpu=026
> <idle>-0 [026] d..2. 13916.282690: sched_switch: prev_comm=swapper/26 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=fio next_pid=766
> 9 next_prio=120
> fio-7669 [026] d..2. 13916.282717: sched_switch: prev_comm=fio prev_pid=7669 prev_prio=120 prev_state=S ==> next_comm=swapper/26 next_pid=
>
>
> This is with added in sched_wakeup_extended() but prev_cpu is not
> correctly assigned yet. Also not needed anymore as we can see
> that migration is in in select_task_rq_fair/sched_migrate_task.
>
The persistent core switches seem to come from select_idle_sibling().
Hmm, that kind of means we should create one queue and ring-thread per
sibling only.
prev parent reply other threads:[~2025-10-19 22:22 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-14 9:49 [PATCH v2] fuse: Wake requests on the same cpu Bernd Schubert
2025-10-14 23:11 ` Joanne Koong
2025-10-15 15:30 ` Bernd Schubert
2025-10-15 16:36 ` Bernd Schubert
2025-10-15 22:19 ` Joanne Koong
2025-10-16 8:58 ` Peter Zijlstra
2025-10-16 9:00 ` Peter Zijlstra
2025-10-16 20:13 ` Joanne Koong
2025-10-16 21:53 ` Bernd Schubert
2025-10-16 22:30 ` Bernd Schubert
2025-10-17 0:01 ` Joanne Koong
2025-10-19 18:15 ` Bernd Schubert
2025-10-19 22:22 ` Bernd Schubert [this message]
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