on 8/1/2023 10:09 AM, Baolin Wang wrote: > > > On 7/29/2023 1:10 AM, Kemeng Shi wrote: >> 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. > > Right. But can you describe the impact in detail if the last_migrated_pfn is not set correctly? For example, this will result in rescan not being set correctly to miss a pageblock's rescanning. > > Otherwise looks good to me. > Sure, the impact will be added in next version. Thanks! >> Update last_migrated_pfn with pageblock_start_pfn(cc->migrate_pfn - 1) >> after scan to correctly set start pfn of last isolated page range. > 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 ce7841363b12..fb250c6b2b6e 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -2482,7 +2482,8 @@ 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, > -- Best wishes Kemeng Shi
