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]
Unified · Split
| @@ -1554,6 +1554,11 @@ struct page *new_page_nodemask(struct page *page, · 1553 unmodified lines | |||
| 1554 | } | 1554 | } |
| 1555 | 1555 | ||
| 1556 | if (PageTransHuge(page)) { | 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 | gfp_mask |= GFP_TRANSHUGE; | 1562 | gfp_mask |= GFP_TRANSHUGE; |
| 1558 | order = HPAGE_PMD_ORDER; | 1563 | order = HPAGE_PMD_ORDER; |
| 1559 | } | 1564 | } |