mm/migrate: clear __GFP_RECLAIM to make the migration callback consistent with regular THP allocations

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]

Joonsoo Kim committed 6 years ago

Commit 9933a0c1 parent d92bbc21 file · +5 −0Browse files

Unified · Split

mm/migrate.c+5−0

@@ -1554,6 +1554,11 @@ struct page new_page_nodemask(struct page page, · 1553 unmodified lines
1554	1554	}
1555	1555
1556	1556	if (PageTransHuge(page)) {
	1557	+ /*
	1558	+ * clear __GFP_RECLAIM to make the migration callback
	1559	+ * consistent with regular THP allocations.
	1560	+ */
	1561	+ gfp_mask &= ~__GFP_RECLAIM;
1557	1562	gfp_mask \|= GFP_TRANSHUGE;
1558	1563	order = HPAGE_PMD_ORDER;
1559	1564	}