mm: compaction: determine if dirty pages can be migrated without blocking within...
authorMel Gorman <mgorman@suse.de>
Fri, 13 Jan 2012 01:19:34 +0000 (17:19 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 13 Jan 2012 04:13:09 +0000 (20:13 -0800)
commitb969c4ab9f182a6e1b2a0848be349f99714947b0
treedc1c6e4375cfec7b15f13a37307eba8a9e07f40f
parent7335084d446b83cbcb15da80497d03f0c1dc9e21
mm: compaction: determine if dirty pages can be migrated without blocking within ->migratepage

Asynchronous compaction is used when allocating transparent hugepages to
avoid blocking for long periods of time.  Due to reports of stalling,
there was a debate on disabling synchronous compaction but this severely
impacted allocation success rates.  Part of the reason was that many dirty
pages are skipped in asynchronous compaction by the following check;

if (PageDirty(page) && !sync &&
mapping->a_ops->migratepage != migrate_page)
rc = -EBUSY;

This skips over all mapping aops using buffer_migrate_page() even though
it is possible to migrate some of these pages without blocking.  This
patch updates the ->migratepage callback with a "sync" parameter.  It is
the responsibility of the callback to fail gracefully if migration would
block.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andy Isaacson <adi@hexapodia.org>
Cc: Nai Xia <nai.xia@gmail.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/btrfs/disk-io.c
fs/hugetlbfs/inode.c
fs/nfs/internal.h
fs/nfs/write.c
include/linux/fs.h
include/linux/migrate.h
mm/migrate.c