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authorMel Gorman <mgorman@techsingularity.net>2019-03-05 15:44:43 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-05 21:07:16 -0800
commit806031bb5ec36ed879d64249d5a5cf9c6657f89d (patch)
tree25a9bc8e338915b0f755701575ee0ec95cf1c110
parent4469ab98477b290f6728b79f8d225d9d88ce16e3 (diff)
mm, migrate: immediately fail migration of a page with no migration handler
Pages with no migration handler use a fallback handler which sometimes works and sometimes persistently retries. A historical example was blockdev pages but there are others such as odd refcounting when page->private is used. These are retried multiple times which is wasteful during compaction so this patch will fail migration faster unless the caller specifies MIGRATE_SYNC. This is not expected to help THP allocation success rates but it did reduce latencies very slightly in some cases. 1-socket thpfioscale 4.20.0 4.20.0 noreserved-v2r15 failfast-v2r15 Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%* Amean fault-both-3 3839.67 ( 0.00%) 3833.72 ( 0.15%) Amean fault-both-5 5177.47 ( 0.00%) 4967.15 ( 4.06%) Amean fault-both-7 7245.03 ( 0.00%) 7139.19 ( 1.46%) Amean fault-both-12 11534.89 ( 0.00%) 11326.30 ( 1.81%) Amean fault-both-18 16241.10 ( 0.00%) 16270.70 ( -0.18%) Amean fault-both-24 19075.91 ( 0.00%) 19839.65 ( -4.00%) Amean fault-both-30 22712.11 ( 0.00%) 21707.05 ( 4.43%) Amean fault-both-32 21692.92 ( 0.00%) 21968.16 ( -1.27%) The 2-socket results are not materially different. Scan rates are similar as expected. Link: http://lkml.kernel.org/r/20190118175136.31341-7-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: David Rientjes <rientjes@google.com> Cc: YueHaibing <yuehaibing@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/migrate.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 0413596fc523..0e9888cb33ad 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -911,7 +911,7 @@ static int fallback_migrate_page(struct address_space *mapping,
*/
if (page_has_private(page) &&
!try_to_release_page(page, GFP_KERNEL))
- return -EAGAIN;
+ return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
return migrate_page(mapping, newpage, page, mode);
}