mm/migrate: clear __GFP_RECLAIM to make the migration callback consistent with regula...

new_page_nodemask is a migration callback and it tries to use a common gfp
flags for the target page allocation whether it is a base page or a THP.
The later only adds GFP_TRANSHUGE to the given mask.  This results in the
allocation being slightly more aggressive than necessary because the
resulting gfp mask will contain also __GFP_RECLAIM_KSWAPD.  THP
allocations usually exclude this flag to reduce over eager background
reclaim during a high THP allocation load which has been seen during large
mmaps initialization.  There is no indication that this is a problem for
migration as well but theoretically the same might happen when migrating
large mappings to a different node.  Make the migration callback
consistent with regular THP allocations.

[akpm@linux-foundation.org: fix comment typo, per Vlastimil]

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Roman Gushchin <guro@fb.com>
Link: http://lkml.kernel.org/r/1594622517-20681-5-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index 8d084e9bc13ba6ea097a42d77eb647a6ea8ac8c2..46cca5c2ebffa8159304c18f0446b3531676b8fe 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1554,6 +1554,11 @@ struct page *new_page_nodemask(struct page *page,
        }
 
        if (PageTransHuge(page)) {
+               /*
+                * clear __GFP_RECLAIM to make the migration callback
+                * consistent with regular THP allocations.
+                */
+               gfp_mask &= ~__GFP_RECLAIM;
                gfp_mask |= GFP_TRANSHUGE;
                order = HPAGE_PMD_ORDER;
        }