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Commit b6136773 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
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[PATCH] schedule_on_each_cpu(): reduce kmalloc() size 



schedule_on_each_cpu() presently does a large kmalloc - 96 kbytes on 1024 CPU
64-bit.

Rework it so that we do one 8192-byte allocation and then a pile of tiny ones,
via alloc_percpu().  This has a much higher chance of success (100% in the
current VM).

This also has the effect of reducing the memory requirements from NR_CPUS*n to
num_possible_cpus()*n.

Cc: Christoph Lameter <clameter@engr.sgi.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 232acbcf

kernel/workqueue.c

+20 −8
Original line number Diff line number Diff line
@@ -428,22 +428,34 @@ int schedule_delayed_work_on(int cpu, 
	return ret;

}



/**

 * schedule_on_each_cpu - call a function on each online CPU from keventd

 * @func: the function to call

 * @info: a pointer to pass to func()

 *

 * Returns zero on success.

 * Returns -ve errno on failure.

 *

 * Appears to be racy against CPU hotplug.

 *

 * schedule_on_each_cpu() is very slow.

 */

int schedule_on_each_cpu(void (*func)(void *info), void *info)

{

	int cpu;

	struct work_struct *work;

	struct work_struct *works;



	work = kmalloc(NR_CPUS * sizeof(struct work_struct), GFP_KERNEL);



	if (!work)

	works = alloc_percpu(struct work_struct);

	if (!works)

		return -ENOMEM;



	for_each_online_cpu(cpu) {

		INIT_WORK(work + cpu, func, info);

		INIT_WORK(per_cpu_ptr(works, cpu), func, info);

		__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),

				work + cpu);

				per_cpu_ptr(works, cpu));

	}

	flush_workqueue(keventd_wq);

	kfree(work);

	free_percpu(works);

	return 0;

}