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From: Marcelo Tosatti <mtosatti@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Nitesh Lal <nilal@redhat.com>,
	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: [patch 0/4] extensible prctl task isolation interface and vmstat sync (v2)
Date: Fri, 30 Jul 2021 17:18:27 -0300	[thread overview]
Message-ID: <20210730201827.269106165@fuller.cnet> (raw)

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, add task isolation prctl interface to quiesce
deferred actions when returning to userspace.

The patchset is based on ideas and code from the
task isolation patchset from Alex Belits:
https://lwn.net/Articles/816298/

Please refer to Documentation/userspace-api/task_isolation.rst
(patch 1) for details.

---------

v2:

- Finer-grained control of quiescing (Frederic Weisbecker / Nicolas Saenz).

- Avoid potential regressions by allowing applications
  to use ISOL_F_QUIESCE_DEFMASK (whose default value
  is configurable in /sys/).         (Nitesh Lal / Nicolas Saenz).


             reply	other threads:[~2021-07-30 20:21 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 20:18 Marcelo Tosatti [this message]
2021-07-30 20:18 ` [patch 1/4] add basic task isolation prctl interface Marcelo Tosatti
     [not found]   ` <CAFki+Lnf0cs62Se0aPubzYxP9wh7xjMXn7RXEPvrmtBdYBrsow@mail.gmail.com>
2021-07-31  0:49     ` Marcelo Tosatti
2021-07-31  7:47   ` kernel test robot
     [not found]   ` <CAFki+LkQVQOe+5aNEKWDvLdnjWjxzKWOiqOvBZzeuPWX+G=XgA@mail.gmail.com>
2021-08-02 14:16     ` Marcelo Tosatti
2021-07-30 20:18 ` [patch 2/4] task isolation: sync vmstats on return to userspace Marcelo Tosatti
2021-08-03 15:13   ` nsaenzju
2021-08-03 16:44     ` Marcelo Tosatti
2021-07-30 20:18 ` [patch 3/4] mm: vmstat: move need_update Marcelo Tosatti
2021-07-30 20:18 ` [patch 4/4] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean Marcelo Tosatti
2021-08-07  2:47   ` Nitesh Lal
2021-08-09 17:34     ` Marcelo Tosatti
2021-08-09 19:13       ` Nitesh Lal
2021-08-10 16:40 ` [patch 0/4] extensible prctl task isolation interface and vmstat sync (v2) Thomas Gleixner
2021-08-10 18:37   ` Marcelo Tosatti
2021-08-10 19:15     ` Marcelo Tosatti

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