From: Andrew Morton <akpm@linux-foundation.org>
To: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
Don Zickus <dzickus@redhat.com>, Ingo Molnar <mingo@kernel.org>,
Andrew Jones <drjones@redhat.com>,
chai wen <chaiw.fnst@cn.fujitsu.com>,
Ulrich Obergfell <uobergfe@redhat.com>,
Fabian Frederick <fabf@skynet.be>,
Aaron Tomlin <atomlin@redhat.com>, Ben Zhang <benzh@chromium.org>,
"Christoph Lameter" <cl@linux.com>,
Gilad Ben-Yossef <gilad@benyossef.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
<linux-kernel@vger.kernel.org>,
"Jonathan Corbet" <corbet@lwn.net>, <linux-doc@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v9 2/3] watchdog: add watchdog_cpumask sysctl to assist nohz
Date: Wed, 29 Apr 2015 15:26:44 -0700 [thread overview]
Message-ID: <20150429152644.5fbe2684f1972a9153d48ec4@linux-foundation.org> (raw)
In-Reply-To: <1429295838-6328-2-git-send-email-cmetcalf@ezchip.com>
On Fri, 17 Apr 2015 14:37:17 -0400 Chris Metcalf <cmetcalf@ezchip.com> wrote:
> Change the default behavior of watchdog so it only runs on the
> housekeeping cores when nohz_full is enabled at build and boot time.
> Allow modifying the set of cores the watchdog is currently running
> on with a new kernel.watchdog_cpumask sysctl.
>
> If we allowed the watchdog to run on nohz_full cores, the timer
> interrupts and scheduler work would prevent the desired tickless
> operation on those cores. But if we disable the watchdog globally,
> then the housekeeping cores can't benefit from the watchdog
> functionality. So we allow disabling it only on some cores.
> See Documentation/lockup-watchdogs.txt for more information.
>
> ...
>
> +watchdog_cpumask:
> +
> +This value can be used to control on which cpus the watchdog may run.
> +The default cpumask is all possible cores, but if NO_HZ_FULL is
> +enabled in the kernel config, and cores are specified with the
> +nohz_full= boot argument, those cores are excluded by default.
> +Offline cores can be included in this mask, and if the core is later
> +brought online, the watchdog will be started based on the mask value.
> +
> +Typically this value would only be touched in the nohz_full case
> +to re-enable cores that by default were not running the watchdog,
> +if a kernel lockup was suspected on those cores.
Now the reader is wondering "how the heck do I specify a cpumask". Is
it hex encoded? decimal? binary string? Which bit corresponds to
which CPU?
A little example would help things along.
next prev parent reply other threads:[~2015-04-29 22:26 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-30 18:51 [PATCH] watchdog: nohz: don't run watchdog on nohz_full cores cmetcalf
2015-03-30 19:12 ` Don Zickus
2015-03-30 19:32 ` [PATCH v2] " Chris Metcalf
2015-03-30 20:02 ` Don Zickus
2015-04-02 15:19 ` Frederic Weisbecker
2015-03-31 2:04 ` [PATCH] " Mike Galbraith
2015-03-31 6:34 ` Mike Galbraith
2015-03-31 18:32 ` Chris Metcalf
2015-03-31 7:25 ` Ingo Molnar
2015-03-31 18:30 ` Chris Metcalf
2015-04-02 13:35 ` Don Zickus
2015-04-02 13:49 ` Chris Metcalf
2015-04-02 14:15 ` Don Zickus
2015-04-02 15:38 ` Frederic Weisbecker
2015-04-02 15:42 ` Chris Metcalf
2015-04-02 16:08 ` Don Zickus
2015-04-02 16:48 ` Frederic Weisbecker
2015-04-02 17:39 ` [PATCH v3] watchdog: add watchdog_cpumask sysctl to assist nohz cmetcalf
2015-04-02 18:06 ` Peter Zijlstra
2015-04-02 18:16 ` Chris Metcalf
2015-04-02 18:33 ` Peter Zijlstra
2015-04-02 18:49 ` Chris Metcalf
2015-04-02 18:45 ` Don Zickus
2015-04-03 16:08 ` [PATCH v4 1/2] smpboot: allow excluding cpus from the smpboot threads cmetcalf
2015-04-03 16:08 ` [PATCH v4 2/2] watchdog: add watchdog_exclude sysctl to assist nohz cmetcalf
2015-04-05 16:46 ` Ulrich Obergfell
2015-04-06 19:45 ` [PATCH v5 0/2] nohz/watchdog/smp_hotplug_thread changes cmetcalf
2015-04-06 19:45 ` [PATCH v5 1/2] smpboot: allow excluding cpus from the smpboot threads cmetcalf
2015-04-08 13:28 ` Frederic Weisbecker
2015-04-08 14:06 ` Chris Metcalf
2015-04-08 17:29 ` Frederic Weisbecker
2015-04-06 19:45 ` [PATCH v5 2/2] watchdog: add watchdog_exclude sysctl to assist nohz cmetcalf
2015-04-07 15:44 ` Don Zickus
2015-04-07 15:56 ` Sasha Levin
2015-04-07 17:49 ` Chris Metcalf
2015-04-08 14:01 ` Frederic Weisbecker
2015-04-08 19:11 ` [PATCH v6 1/2] smpboot: allow excluding cpus from the smpboot threads cmetcalf
2015-04-08 19:11 ` [PATCH v6 2/2] watchdog: add watchdog_cpumask sysctl to assist nohz cmetcalf
2015-04-08 20:37 ` [PATCH v6 1/2] smpboot: allow excluding cpus from the smpboot threads Thomas Gleixner
2015-04-09 20:29 ` [PATCH] " Chris Metcalf
2015-04-10 1:58 ` Frederic Weisbecker
2015-04-10 16:33 ` Chris Metcalf
2015-04-12 19:14 ` Frederic Weisbecker
2015-04-13 16:06 ` Chris Metcalf
2015-04-13 21:54 ` Frederic Weisbecker
2015-04-14 19:37 ` [PATCH v8 1/3] " Chris Metcalf
2015-04-14 19:37 ` [PATCH v8 2/3] watchdog: add watchdog_cpumask sysctl to assist nohz Chris Metcalf
2015-04-16 10:46 ` Ulrich Obergfell
2015-04-17 15:41 ` Chris Metcalf
2015-04-22 8:20 ` Ulrich Obergfell
2015-04-28 17:52 ` Chris Metcalf
2015-04-29 8:48 ` Ulrich Obergfell
2015-04-17 1:31 ` Chai Wen
2015-04-17 16:10 ` Chris Metcalf
2015-04-14 19:37 ` [PATCH v8 3/3] procfs: treat parked tasks as sleeping for task state Chris Metcalf
2015-04-16 15:28 ` [PATCH v8 1/3] smpboot: allow excluding cpus from the smpboot threads Frederic Weisbecker
2015-04-16 15:50 ` Chris Metcalf
2015-04-16 16:48 ` Frederic Weisbecker
2015-04-17 16:17 ` Chris Metcalf
2015-04-17 18:37 ` [PATCH v9 " Chris Metcalf
2015-04-17 18:37 ` [PATCH v9 2/3] watchdog: add watchdog_cpumask sysctl to assist nohz Chris Metcalf
2015-04-21 12:32 ` Ulrich Obergfell
2015-04-28 18:07 ` Chris Metcalf
2015-04-29 9:49 ` Ulrich Obergfell
2015-04-29 13:10 ` Don Zickus
2015-04-21 14:07 ` Ulrich Obergfell
2015-04-22 15:18 ` Don Zickus
2015-04-25 15:42 ` Ulrich Obergfell
2015-04-22 11:02 ` Ulrich Obergfell
2015-04-22 15:21 ` Don Zickus
2015-04-27 20:27 ` Chris Metcalf
2015-04-28 15:17 ` Don Zickus
2015-04-28 19:42 ` Andrew Morton
2015-04-30 19:39 ` [PATCH v10 0/3] add watchdog_cpumask to help nohz_full Chris Metcalf
2015-04-30 19:39 ` [PATCH v10 1/3] smpboot: allow excluding cpus from the smpboot threads Chris Metcalf
2015-05-01 8:53 ` Frederic Weisbecker
2015-05-01 19:57 ` Chris Metcalf
2015-05-01 21:23 ` Frederic Weisbecker
2015-05-04 22:06 ` Chris Metcalf
2015-06-03 2:34 ` Don Zickus
2015-06-04 17:25 ` Chris Metcalf
2015-05-01 20:00 ` [PATCH] smpboot: dynamically allocate the cpumask Chris Metcalf
2015-04-30 19:39 ` [PATCH v10 2/3] watchdog: add watchdog_cpumask sysctl to assist nohz Chris Metcalf
2015-04-30 20:00 ` Don Zickus
2015-04-30 20:09 ` Chris Metcalf
2015-05-01 13:46 ` Don Zickus
2015-04-30 19:39 ` [PATCH v10 3/3] procfs: treat parked tasks as sleeping for task state Chris Metcalf
2015-04-29 22:26 ` [PATCH v9 2/3] watchdog: add watchdog_cpumask sysctl to assist nohz Andrew Morton
2015-04-29 22:26 ` Andrew Morton [this message]
2015-04-17 18:37 ` [PATCH v9 3/3] procfs: treat parked tasks as sleeping for task state Chris Metcalf
2015-04-29 22:26 ` Andrew Morton
2015-04-29 22:26 ` [PATCH v9 1/3] smpboot: allow excluding cpus from the smpboot threads Andrew Morton
2015-04-30 16:07 ` Chris Metcalf
2015-04-14 15:23 ` [PATCH] " Frederic Weisbecker
2015-04-14 15:39 ` Chris Metcalf
2015-04-14 17:57 ` Thomas Gleixner
2015-04-10 20:48 ` [PATCH v7 1/3] " Chris Metcalf
2015-04-10 20:48 ` [PATCH v7 2/3] watchdog: add watchdog_cpumask sysctl to assist nohz Chris Metcalf
2015-04-10 20:48 ` [PATCH v7 3/3] procfs: treat parked tasks as sleeping for task state Chris Metcalf
2015-04-10 21:11 ` [PATCH v7 1/3] smpboot: allow excluding cpus from the smpboot threads Andrew Morton
2015-04-13 15:48 ` Chris Metcalf
2015-04-08 19:21 ` [PATCH v5 2/2] watchdog: add watchdog_exclude sysctl to assist nohz Chris Metcalf
2015-04-08 22:31 ` Frederic Weisbecker
2015-03-31 10:17 ` [PATCH] watchdog: nohz: don't run watchdog on nohz_full cores Christoph Lameter
2015-03-31 18:39 ` Chris Metcalf
2015-04-02 14:13 ` Christoph Lameter
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