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.
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,
