• Mel Gorman's avatar
    mm: avoid unnecessary atomic operations during end_page_writeback() · 888cf2db
    Mel Gorman authored
    If a page is marked for immediate reclaim then it is moved to the tail of
    the LRU list.  This occurs when the system is under enough memory pressure
    for pages under writeback to reach the end of the LRU but we test for this
    using atomic operations on every writeback.  This patch uses an optimistic
    non-atomic test first.  It'll miss some pages in rare cases but the
    consequences are not severe enough to warrant such a penalty.
    While the function does not dominate profiles during a simple dd test the
    cost of it is reduced.
    73048     0.7428  vmlinux-3.15.0-rc5-mmotm-20140513 end_page_writeback
    23740     0.2409  vmlinux-3.15.0-rc5-lessatomic     end_page_writeback
    Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
filemap.c 71.6 KB