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From: Marcelo Tosatti <mtosatti@redhat.com>
To: Nitesh Lal <nilal@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 14:32:04 -0300	[thread overview]
Message-ID: <20210901173204.GA48995@fuller.cnet> (raw)
In-Reply-To: <CAFki+LkNcwFATSth4cvU=-7aBZjaLLNU6UFWYv1DxkeYwkeuSg@mail.gmail.com>

On Wed, Sep 01, 2021 at 09:05:55AM -0400, Nitesh Lal wrote:
> 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.

Hi Nitesh,

Did you use chisol (with proper flags) and the modified oslat?

Tested with "echo 1 > /proc/sys/vmstat_refresh" and it was successful
(no hangs).

> 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.

No, that can happen. Can use sched notifiers to handle this problem.
Good point.


  reply	other threads:[~2021-09-01 17:38 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
2021-09-01 17:32     ` Marcelo Tosatti [this message]
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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