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Subject[PATCH v1 2/6] workqueue: introduce schedule_on_each_cpu_mask
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Introduce schedule_on_each_cpu_mask function to schedule a work
item on each online CPU which is included in the mask provided.

Then re-implement schedule_on_each_cpu on top of the new function.

This function should be prefered to schedule_on_each_cpu in
any case where some of the CPUs, especially on a big multi-core
system, might not have actual work to perform in order to save
needless wakeups and schedules.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Tejun Heo <tj@kernel.org>
CC: John Stultz <johnstul@us.ibm.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Mel Gorman <mel@csn.ul.ie>
CC: Mike Frysinger <vapier@gentoo.org>
CC: David Rientjes <rientjes@google.com>
CC: Hugh Dickins <hughd@google.com>
CC: Minchan Kim <minchan.kim@gmail.com>
CC: Konstantin Khlebnikov <khlebnikov@openvz.org>
CC: Christoph Lameter <cl@linux.com>
CC: Chris Metcalf <cmetcalf@tilera.com>
CC: Hakan Akkan <hakanakkan@gmail.com>
CC: Max Krasnyansky <maxk@qualcomm.com>
CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: linux-kernel@vger.kernel.org
CC: linux-mm@kvack.org
---
include/linux/workqueue.h | 2 ++
kernel/workqueue.c | 36 ++++++++++++++++++++++++++++--------
2 files changed, 30 insertions(+), 8 deletions(-)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index af15545..20da95a 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -383,6 +383,8 @@ extern int schedule_delayed_work(struct delayed_work *work, unsigned long delay)
extern int schedule_delayed_work_on(int cpu, struct delayed_work *work,
unsigned long delay);
extern int schedule_on_each_cpu(work_func_t func);
+extern int schedule_on_each_cpu_mask(work_func_t func,
+ const struct cpumask *mask);
extern int keventd_up(void);

int execute_in_process_context(work_func_t fn, struct execute_work *);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 5abf42f..1c9782b 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2787,43 +2787,63 @@ int schedule_delayed_work_on(int cpu,
EXPORT_SYMBOL(schedule_delayed_work_on);

/**
- * schedule_on_each_cpu - execute a function synchronously on each online CPU
+ * schedule_on_each_cpu_mask - execute a function synchronously on each
+ * online CPU which is specified in the supplied cpumask
* @func: the function to call
+ * @mask: the cpu mask
*
- * schedule_on_each_cpu() executes @func on each online CPU using the
- * system workqueue and blocks until all CPUs have completed.
- * schedule_on_each_cpu() is very slow.
+ * schedule_on_each_cpu_mask() executes @func on each online CPU which
+ * is part of the @mask using the * system workqueue and blocks until
+ * all CPUs have completed
+ * schedule_on_each_cpu_mask() is very slow.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
-int schedule_on_each_cpu(work_func_t func)
+int schedule_on_each_cpu_mask(work_func_t func, const struct cpumask *mask)
{
int cpu;
struct work_struct __percpu *works;

works = alloc_percpu(struct work_struct);
- if (!works)
+ if (unlikely(!works))
return -ENOMEM;

get_online_cpus();

- for_each_online_cpu(cpu) {
+ for_each_cpu_and(cpu, mask, cpu_online_mask) {
struct work_struct *work = per_cpu_ptr(works, cpu);

INIT_WORK(work, func);
schedule_work_on(cpu, work);
}

- for_each_online_cpu(cpu)
+ for_each_cpu_and(cpu, mask, cpu_online_mask)
flush_work(per_cpu_ptr(works, cpu));

put_online_cpus();
free_percpu(works);
+
return 0;
}

/**
+ * schedule_on_each_cpu - execute a function synchronously on each online CPU
+ * @func: the function to call
+ *
+ * schedule_on_each_cpu() executes @func on each online CPU using the
+ * system workqueue and blocks until all CPUs have completed.
+ * schedule_on_each_cpu() is very slow.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int schedule_on_each_cpu(work_func_t func)
+{
+ return schedule_on_each_cpu_mask(func, cpu_online_mask);
+}
+
+/**
* flush_scheduled_work - ensure that any scheduled work has run to completion.
*
* Forces execution of the kernel-global workqueue and blocks until its
--
1.7.0.4


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