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authorChris Metcalf <cmetcalf@ezchip.com>2015-06-25 01:55:42 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-25 02:49:40 +0200
commitb5242e98c1cb834feb1e84026f09a4796b49eb4d (patch)
tree46f415a3fb41a6238f8e6d69675d2e22960c3447 /kernel/sysctl.c
parentsparc: use for_each_sg() (diff)
downloadlinux-b5242e98c1cb834feb1e84026f09a4796b49eb4d.tar.xz
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smpboot: allow excluding cpus from the smpboot threads
This patch series allows the watchdog to run by default only on the housekeeping cores when nohz_full is in effect; this seems to be a good compromise short of turning it off completely (since the nohz_full cores can't tolerate a watchdog). To provide customizability, we add /proc/sys/kernel/watchdog_cpumask so that the set of cores running the watchdog can be tuned to different values after bootup. To implement this customizability, we add a new smpboot_update_cpumask_percpu_thread() API to the smpboot_thread subsystem that lets us park or unpark "unwanted" threads. And now that threads can be parked for long periods of time, we tweak the /proc/<pid>/stat and /proc/<pid>/status code so parked threads aren't reported as running, which is otherwise confusing. This patch (of 3): This change allows some cores to be excluded from running the smp_hotplug_thread tasks. The following commit to update kernel/watchdog.c to use this functionality is the motivating example, and more information on the motivation is provided there. A new smp_hotplug_thread field is introduced, "cpumask", which is cpumask field managed by the smpboot subsystem that indicates whether or not the given smp_hotplug_thread should run on that core; the cpumask is checked when deciding whether to unpark the thread. To limit the cpumask to less than cpu_possible, you must call smpboot_update_cpumask_percpu_thread() after registering. Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com> Cc: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sysctl.c')
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