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From: Nitesh Lal <nilal@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: linux-kernel@vger.kernel.org,
	Nicolas Saenz Julienne <nsaenzju@redhat.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Christoph Lameter <cl@linux.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Alex Belits <abelits@belits.com>, Peter Xu <peterx@redhat.com>
Subject: Re: [patch V3 8/8] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean
Date: Wed, 1 Sep 2021 09:05:55 -0400	[thread overview]
Message-ID: <CAFki+LkNcwFATSth4cvU=-7aBZjaLLNU6UFWYv1DxkeYwkeuSg@mail.gmail.com> (raw)
In-Reply-To: <20210824152646.948424573@fuller.cnet>

Hi Marcelo,

On Tue, Aug 24, 2021 at 11:42 AM Marcelo Tosatti <mtosatti@redhat.com> wrote:
>
> It is not necessary to queue work item to run refresh_vm_stats
> on a remote CPU if that CPU has no dirty stats and no per-CPU
> allocations for remote nodes.
>
> This fixes sosreport hang (which uses vmstat_refresh) with
> spinning SCHED_FIFO process.
>

I was still able to reproduce the sosreport hang with this patchset and I
am wondering if that is because right now we do vmstat_sync and then cancel
any pending jobs on a CPU in the context of one task.

However, while this task is running another process can come in and can
dirty the stats resulting in vmstat job getting placed on CPUs running
SCHED_FIFO tasks.
Am I missing something?

What we can probably do is to communicate that a CPU is running on task
isolation mode to any other process that is trying to run and schedule
jobs there.

-- 
Thanks
Nitesh


  parent reply	other threads:[~2021-09-01 13:06 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24 15:24 [patch V3 0/8] extensible prctl task isolation interface and vmstat sync Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 1/8] add basic task isolation prctl interface Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 2/8] add prctl task isolation prctl docs and samples Marcelo Tosatti
2021-08-26  9:59   ` Frederic Weisbecker
2021-08-26 12:11     ` Marcelo Tosatti
2021-08-26 19:15       ` Christoph Lameter
2021-08-26 20:37         ` Marcelo Tosatti
2021-08-27 13:08       ` Frederic Weisbecker
2021-08-27 14:44         ` Marcelo Tosatti
2021-08-30 11:38           ` Frederic Weisbecker
2021-09-01 13:11   ` Nitesh Lal
2021-09-01 17:34     ` Marcelo Tosatti
2021-09-01 17:49       ` Nitesh Lal
2021-08-24 15:24 ` [patch V3 3/8] task isolation: sync vmstats on return to userspace Marcelo Tosatti
2021-09-10 13:49   ` nsaenzju
2021-08-24 15:24 ` [patch V3 4/8] procfs: add per-pid task isolation state Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 5/8] task isolation: sync vmstats conditional on changes Marcelo Tosatti
2021-08-25  9:46   ` Christoph Lameter
2021-08-24 15:24 ` [patch V3 6/8] KVM: x86: call isolation prepare from VM-entry code path Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 7/8] mm: vmstat: move need_update Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 8/8] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean Marcelo Tosatti
2021-08-25  9:30   ` Christoph Lameter
2021-09-01 13:05   ` Nitesh Lal [this message]
2021-09-01 17:32     ` Marcelo Tosatti
2021-09-01 18:33       ` Marcelo Tosatti
2021-09-03 17:38         ` Nitesh Lal
2021-08-25 10:02 ` [patch V3 0/8] extensible prctl task isolation interface and vmstat sync Marcelo Tosatti

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