Commit 2f60d628 authored Sep 28, 2012 by Srivatsa S. Bhat Committed by Fengguang Wu Sep 28, 2012

CPU hotplug, writeback: Don't call writeback_set_ratelimit() too often during hotplug

The CPU hotplug callback related to writeback calls writeback_set_ratelimit()
during every state change in the hotplug sequence. This is unnecessary
since num_online_cpus() changes only once during the entire hotplug operation.

So invoke the function only once per hotplug, thereby avoiding the
unnecessary repetition of those costly calculations.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

parent 0e2f2b23

mm/page-writeback.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -1602,11 +1602,19 @@ void writeback_set_ratelimit(void)
		}

		static int __cpuinit
		ratelimit_handler(struct notifier_block self, unsigned long u, void v)
		ratelimit_handler(struct notifier_block *self, unsigned long action,
		void *hcpu)
		{

		switch (action & ~CPU_TASKS_FROZEN) {
		case CPU_ONLINE:
		case CPU_DEAD:
		writeback_set_ratelimit();
		return NOTIFY_OK;
		default:
		return NOTIFY_DONE;
		}
		}

		static struct notifier_block __cpuinitdata ratelimit_nb = {
		.notifier_call = ratelimit_handler,