tree 03a55a0eb6bc7fbf4778539d26fc3be8f8ec9d52
parent 0bd62b1190607e4f1b3c2927ba48672a1cf2a83d
author Mel Gorman <mgorman@suse.de> 1401923405 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1401926048 -0700

mm: page_alloc: do not update zlc unless the zlc is active

The zlc is used on NUMA machines to quickly skip over zones that are full.
 However it is always updated, even for the first zone scanned when the
zlc might not even be active.  As it's a write to a bitmap that
potentially bounces cache line it's deceptively expensive and most
machines will not care.  Only update the zlc if it was active.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>