We record start pfn of last isolated page block with last_migrated_pfn. And then: 1. We check if we mark the page block skip for exclusive access in isolate_migratepages_block by test if next migrate pfn is still in last isolated page block. If so, we will set finish_pageblock to do the rescan. 2. We check if a full cc->order block is scanned by test if last scan range passes the cc->order block boundary. If so, we flush the pages were freed. We treat cc->migrate_pfn before isolate_migratepages as the start pfn of last isolated page range. However, we always align migrate_pfn to page block or move to another page block in fast_find_migrateblock or in linearly scan forward in isolate_migratepages before do page isolation in isolate_migratepages_block. Update last_migrated_pfn with pageblock_start_pfn(cc->migrate_pfn - 1) after scan to correctly set start pfn of last isolated page range. To avoid that: 1. Miss a rescan with finish_pageblock set as last_migrate_pfn does not point to right pageblock and the migrate will not be in pageblock of last_migrate_pfn as it should be. 2. Wrongly issue flush by test cc->order block boundary with wrong last_migrate_pfn. Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx> --- mm/compaction.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index a8cea916df9d..ec3a96b7afce 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -2487,7 +2487,8 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) goto check_drain; case ISOLATE_SUCCESS: update_cached = false; - last_migrated_pfn = iteration_start_pfn; + last_migrated_pfn = max(cc->zone->zone_start_pfn, + pageblock_start_pfn(cc->migrate_pfn - 1)); } err = migrate_pages(&cc->migratepages, compaction_alloc, -- 2.30.0
