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>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 5ad5ce2..830893b 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1602,10 +1602,18 @@
}
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 = {