From: Frederic Weisbecker <frederic@kernel.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: linux-kernel@vger.kernel.org, Christoph Lameter <cl@linux.com>,
Thomas Gleixner <tglx@linutronix.de>,
Juri Lelli <juri.lelli@redhat.com>, Nitesh Lal <nilal@redhat.com>
Subject: Re: [patch 0/5] optionally sync per-CPU vmstats counter on return to userspace
Date: Fri, 2 Jul 2021 14:30:32 +0200 [thread overview]
Message-ID: <20210702123032.GA72061@lothringen> (raw)
In-Reply-To: <20210701210336.358118649@fuller.cnet>
On Thu, Jul 01, 2021 at 06:03:36PM -0300, Marcelo Tosatti wrote:
> The logic to disable vmstat worker thread, when entering
> nohz full, does not cover all scenarios. For example, it is possible
> for the following to happen:
>
> 1) enter nohz_full, which calls refresh_cpu_vm_stats, syncing the stats.
> 2) app runs mlock, which increases counters for mlock'ed pages.
> 3) start -RT loop
>
> Since refresh_cpu_vm_stats from nohz_full logic can happen _before_
> the mlock, vmstat shepherd can restart vmstat worker thread on
> the CPU in question.
>
> To fix this, optionally sync the vmstat counters when returning
> from userspace, controllable by a new "vmstat_sync" isolcpus
> flags (default off).
Wasn't the plan for such finegrained isolation features to do it at
the per task level using prctl()?
Thanks.
>
> See individual patches for details.
>
>
next prev parent reply other threads:[~2021-07-02 12:30 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-01 21:03 [patch 0/5] optionally sync per-CPU vmstats counter on return to userspace Marcelo Tosatti
2021-07-01 21:03 ` [patch 1/5] sched: isolation: introduce vmstat_sync isolcpu flags Marcelo Tosatti
2021-07-01 21:03 ` [patch 2/5] common entry: add hook for isolation to __syscall_exit_to_user_mode_work Marcelo Tosatti
2021-07-01 21:03 ` [patch 3/5] mm: vmstat: optionally flush per-CPU vmstat counters on return to userspace Marcelo Tosatti
2021-07-01 23:11 ` kernel test robot
2021-07-02 6:50 ` kernel test robot
2021-07-01 21:03 ` [patch 4/5] mm: vmstat: move need_update Marcelo Tosatti
2021-07-01 21:03 ` [patch 5/5] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean Marcelo Tosatti
2021-07-02 4:10 ` kernel test robot
2021-07-02 4:43 ` kernel test robot
2021-07-02 8:00 ` [patch 0/5] optionally sync per-CPU vmstats counter on return to userspace Christoph Lameter
2021-07-02 11:52 ` Marcelo Tosatti
2021-07-02 11:59 ` Marcelo Tosatti
2021-07-05 14:26 ` Christoph Lameter
2021-07-05 14:45 ` Marcelo Tosatti
2021-07-02 12:30 ` Frederic Weisbecker [this message]
2021-07-02 15:28 ` Marcelo Tosatti
2021-07-06 13:09 ` Frederic Weisbecker
2021-07-06 14:05 ` Marcelo Tosatti
2021-07-06 14:09 ` Marcelo Tosatti
2021-07-06 14:17 ` Marcelo Tosatti
2021-07-06 16:15 ` Peter Zijlstra
2021-07-06 16:53 ` Marcelo Tosatti
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