From 2f60d628ffd042e65e0b1d3431fb3e38d6f7c1be Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Fri, 28 Sep 2012 20:27:49 +0800 Subject: [PATCH] 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 --- mm/page-writeback.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 5ad5ce23c1e0..830893b2b3c7 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1602,10 +1602,18 @@ 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) { - writeback_set_ratelimit(); - return NOTIFY_DONE; + + 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 = {