From: Vlastimil Babka <vbabka@suse.cz>
Date: Wed, 11 Sep 2013 21:22:33 +0000 (-0700)
Subject: mm: munlock: remove redundant get_page/put_page pair on the fast path
X-Git-Tag: v3.12-rc1~52^2~187
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5b40998ae35cf64561868370e6c9f3d3e94b6bf7;p=pandora-kernel.git

mm: munlock: remove redundant get_page/put_page pair on the fast path

The performance of the fast path in munlock_vma_range() can be further
improved by avoiding atomic ops of a redundant get_page()/put_page() pair.

When calling get_page() during page isolation, we already have the pin
from follow_page_mask().  This pin will be then returned by
__pagevec_lru_add(), after which we do not reference the pages anymore.

After this patch, an 8% speedup was measured for munlocking a 56GB large
memory area with THP disabled.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jörn Engel <joern@logfs.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

Reading git-diff-tree failed