diff options
| -rw-r--r-- | mm/compaction.c | 47 |
1 files changed, 27 insertions, 20 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 0dce7e87d771..1ccb015ab1eb 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -680,6 +680,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, /* Time to isolate some pages for migration */ for (; low_pfn < end_pfn; low_pfn++) { + bool is_lru; + /* * Periodically drop the lock (if held) regardless of its * contention, to give chance to IRQs. Abort async compaction @@ -723,36 +725,35 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, * It's possible to migrate LRU pages and balloon pages * Skip any other type of page */ - if (!PageLRU(page)) { + is_lru = PageLRU(page); + if (!is_lru) { if (unlikely(balloon_page_movable(page))) { if (balloon_page_isolate(page)) { /* Successfully isolated */ goto isolate_success; } } - continue; } /* - * PageLRU is set. lru_lock normally excludes isolation - * splitting and collapsing (collapsing has already happened - * if PageLRU is set) but the lock is not necessarily taken - * here and it is wasteful to take it just to check transhuge. - * Check TransHuge without lock and skip the whole pageblock if - * it's either a transhuge or hugetlbfs page, as calling - * compound_order() without preventing THP from splitting the - * page underneath us may return surprising results. + * Regardless of being on LRU, compound pages such as THP and + * hugetlbfs are not to be compacted. We can potentially save + * a lot of iterations if we skip them at once. The check is + * racy, but we can consider only valid values and the only + * danger is skipping too much. */ - if (PageTransHuge(page)) { - if (!locked) - low_pfn = ALIGN(low_pfn + 1, - pageblock_nr_pages) - 1; - else - low_pfn += (1 << compound_order(page)) - 1; + if (PageCompound(page)) { + unsigned int comp_order = compound_order(page); + + if (likely(comp_order < MAX_ORDER)) + low_pfn += (1UL << comp_order) - 1; continue; } + if (!is_lru) + continue; + /* * Migration will fail if an anonymous page is pinned in memory, * so avoid taking lru_lock and isolating it unnecessarily in an @@ -769,11 +770,17 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (!locked) break; - /* Recheck PageLRU and PageTransHuge under lock */ + /* Recheck PageLRU and PageCompound under lock */ if (!PageLRU(page)) continue; - if (PageTransHuge(page)) { - low_pfn += (1 << compound_order(page)) - 1; + + /* + * Page become compound since the non-locked check, + * and it's on LRU. It can only be a THP so the order + * is safe to read and it's 0 for tail pages. + */ + if (unlikely(PageCompound(page))) { + low_pfn += (1UL << compound_order(page)) - 1; continue; } } @@ -784,7 +791,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (__isolate_lru_page(page, isolate_mode) != 0) continue; - VM_BUG_ON_PAGE(PageTransCompound(page), page); + VM_BUG_ON_PAGE(PageCompound(page), page); /* Successfully isolated */ del_page_from_lru_list(page, lruvec, page_lru(page)); |