From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Steve Muckle <smuckle@google.com>, Wanpeng Li <kernellwp@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Miguel de Dios <migueldedios@google.com>,
Ingo Molnar <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team@android.com, Todd Kjos <tkjos@google.com>,
Paul Turner <pjt@google.com>,
quentin.perret@arm.com, Patrick Bellasi <Patrick.Bellasi@arm.com>,
Chris.Redpath@arm.com,
Morten Rasmussen <Morten.Rasmussen@arm.com>,
John Dias <joaodias@google.com>,
Wanpeng Li <wanpengli@tencent.com>
Subject: Re: [PATCH] sched/fair: vruntime should normalize when switching from fair
Date: Fri, 28 Sep 2018 19:35:53 +0200 [thread overview]
Message-ID: <2cee0f7c-023d-7b20-0a19-c2a4427625d9@arm.com> (raw)
In-Reply-To: <c0ec8322-4256-d8ae-0978-25ab44e34d68@google.com>
On 09/28/2018 06:10 PM, Steve Muckle wrote:
> On 09/27/2018 05:43 PM, Wanpeng Li wrote:
>>>> On your CPU4:
>>>> scheduler_ipi()
>>>> -> sched_ttwu_pending()
>>>> -> ttwu_do_activate() => p->sched_remote_wakeup should be
>>>> false, so ENQUEUE_WAKEUP is set, ENQUEUE_MIGRATED is not
>>>> -> ttwu_activate()
>>>> -> activate_task()
>>>> -> enqueue_task()
>>>> -> enqueue_task_fair()
>>>> -> enqueue_entity()
>>>> bool renorm = !(flags &
>>>> ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATE)
>>>> so renorm is false in enqueue_entity(), why you mentioned that the
>>>> cfs_rq->min_vruntime is still added to the se->vruntime in
>>>> enqueue_task_fair()?
>>>
>>> Maybe this is a misunderstanding on my side but didn't you asked me to
>>> '... Could you point out when the fair rq's min_vruntime is added to the
>>> task's vruntime in your *later* scenario? ...'
>>
>> Yeah, if the calltrace above and my analysis is correct, then the fair
>> rq's min_vruntime will not be added to the task's vruntime in your
>> *later* scenario, which means that your patch is not necessary.
>
> In the scenario I observed, the task is not waking - it is running and
> being deboosted from priority inheritance, transitioning from RT to CFS.
>
> Dietmar and I both were able to reproduce the issue with the testcase I
> posted earlier in this thread.
Correct, and with the same testcase I got this call stack in this scenario:
[ 35.588509] CPU: 1 PID: 2926 Comm: fair_task Not tainted
4.18.0-rc6-00052-g11b7dafa2edb-dirty #5
[ 35.597217] Hardware name: ARM Juno development board (r0) (DT)
[ 35.603080] Call trace:
[ 35.605509] dump_backtrace+0x0/0x168
[ 35.609138] show_stack+0x24/0x30
[ 35.612424] dump_stack+0xac/0xe4
[ 35.615710] enqueue_task_fair+0xae0/0x11c0
[ 35.619854] rt_mutex_setprio+0x5a0/0x628
[ 35.623827] mark_wakeup_next_waiter+0x7c/0xc8
[ 35.628228] __rt_mutex_futex_unlock+0x30/0x50
[ 35.632630] do_futex+0x74c/0xb28
[ 35.635912] sys_futex+0x118/0x198
[ 35.639280] el0_svc_naked+0x30/0x34
[...]
next prev parent reply other threads:[~2018-09-28 17:36 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-17 18:27 [PATCH] sched/fair: vruntime should normalize when switching from fair Steve Muckle
2018-08-20 23:54 ` Miguel de Dios
2018-08-23 16:52 ` Dietmar Eggemann
2018-08-24 6:54 ` Juri Lelli
2018-08-24 21:17 ` Steve Muckle
2018-09-06 23:25 ` Dietmar Eggemann
2018-09-07 7:16 ` Juri Lelli
2018-09-07 7:58 ` Vincent Guittot
2018-09-11 6:24 ` Dietmar Eggemann
2018-08-24 9:32 ` Peter Zijlstra
2018-08-24 9:47 ` Peter Zijlstra
2018-08-24 21:24 ` Steve Muckle
2018-08-27 11:14 ` Peter Zijlstra
2018-08-28 14:53 ` Dietmar Eggemann
2018-08-29 10:54 ` Dietmar Eggemann
2018-08-29 11:59 ` Peter Zijlstra
2018-08-29 15:33 ` Dietmar Eggemann
2018-08-31 22:24 ` Steve Muckle
2018-09-26 9:50 ` Wanpeng Li
2018-09-26 22:38 ` Dietmar Eggemann
2018-09-27 1:19 ` Wanpeng Li
2018-09-27 13:22 ` Dietmar Eggemann
2018-09-28 0:43 ` Wanpeng Li
2018-09-28 16:10 ` Steve Muckle
2018-09-28 16:45 ` Joel Fernandes
2018-09-28 17:35 ` Dietmar Eggemann [this message]
2018-09-29 1:07 ` Wanpeng Li
2018-09-28 17:11 ` Dietmar Eggemann
2018-09-28 16:43 ` Joel Fernandes
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