linux-kernel - [PATCH 2/8] mm/compaction: correct last_migrated_pfn update in compact

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Message-Id: <20230728171037.2219226-3-shikemeng@huaweicloud.com>
Date:   Sat, 29 Jul 2023 01:10:31 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, baolin.wang@...ux.alibaba.com,
        mgorman@...hsingularity.net, willy@...radead.org, david@...hat.com
Cc:     shikemeng@...weicloud.com
Subject: [PATCH 2/8] mm/compaction: correct last_migrated_pfn update in compact_zone

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.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
---
 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,
-- 
2.30.0