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author | Chris Metcalf <cmetcalf@ezchip.com> | 2015-06-24 16:55:42 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-06-24 17:49:40 -0700 |
commit | b5242e98c1cb834feb1e84026f09a4796b49eb4d (patch) | |
tree | 46f415a3fb41a6238f8e6d69675d2e22960c3447 /include | |
parent | 8c07a308ec5284fe41aefe48ac2ef4cfcd71ddbf (diff) | |
download | linux-b5242e98c1cb834feb1e84026f09a4796b49eb4d.tar.gz linux-b5242e98c1cb834feb1e84026f09a4796b49eb4d.tar.bz2 linux-b5242e98c1cb834feb1e84026f09a4796b49eb4d.zip |
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 'include')
-rw-r--r-- | include/linux/smpboot.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h index d600afb21926..da3c593f9845 100644 --- a/include/linux/smpboot.h +++ b/include/linux/smpboot.h @@ -27,6 +27,8 @@ struct smpboot_thread_data; * @pre_unpark: Optional unpark function, called before the thread is * unparked (cpu online). This is not guaranteed to be * called on the target cpu of the thread. Careful! + * @cpumask: Internal state. To update which threads are unparked, + * call smpboot_update_cpumask_percpu_thread(). * @selfparking: Thread is not parked by the park function. * @thread_comm: The base name of the thread */ @@ -41,11 +43,14 @@ struct smp_hotplug_thread { void (*park)(unsigned int cpu); void (*unpark)(unsigned int cpu); void (*pre_unpark)(unsigned int cpu); + cpumask_var_t cpumask; bool selfparking; const char *thread_comm; }; int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread); void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread); +int smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread, + const struct cpumask *); #endif |