2023-05-15 11:40:26

by Mel Gorman

Subject: [PATCH 1/4] mm: compaction: Ensure rescanning only happens on partially scanned pageblocks

compact_zone() intends to rescan pageblocks if there is a failure to
migrate "within the current order-aligned block". However, the pageblock
scan may already be complete and moved to the next block causing the
next pageblock to be "rescanned". Ensure only the most recent pageblock
is rescanned.

Reported-by: Vlastimil Babka <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
---
mm/compaction.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index c8bcdea15f5f..81791c124bb8 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2464,8 +2464,9 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
* fast_find_migrateblock revisiting blocks that were
* recently partially scanned.
*/
- if (cc->direct_compaction && !cc->finish_pageblock &&
- (cc->mode < MIGRATE_SYNC)) {
+ if (!pageblock_aligned(cc->migrate_pfn) &&
+ cc->direct_compaction && !cc->finish_pageblock &&
+ (cc->mode < MIGRATE_SYNC)) {
cc->finish_pageblock = true;

/*
--
2.35.3

2023-05-25 10:32:54

by Vlastimil Babka

Subject: Re: [PATCH 1/4] mm: compaction: Ensure rescanning only happens on partially scanned pageblocks

On 5/15/23 13:33, Mel Gorman wrote:
> compact_zone() intends to rescan pageblocks if there is a failure to
> migrate "within the current order-aligned block". However, the pageblock
> scan may already be complete and moved to the next block causing the
> next pageblock to be "rescanned". Ensure only the most recent pageblock
> is rescanned.
>
> Reported-by: Vlastimil Babka <[email protected]>
> Signed-off-by: Mel Gorman <[email protected]>

Acked-by: Vlastimil Babka <[email protected]>

> ---
> mm/compaction.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index c8bcdea15f5f..81791c124bb8 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2464,8 +2464,9 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
> * fast_find_migrateblock revisiting blocks that were
> * recently partially scanned.
> */
> - if (cc->direct_compaction && !cc->finish_pageblock &&
> - (cc->mode < MIGRATE_SYNC)) {
> + if (!pageblock_aligned(cc->migrate_pfn) &&
> + cc->direct_compaction && !cc->finish_pageblock &&
> + (cc->mode < MIGRATE_SYNC)) {
> cc->finish_pageblock = true;
>
> /*