linux-kernel - [PATCH v2 2/2] mm/compaction: stop isolation if too many pages are isolated and we have pages to migrate.

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Date:   Fri, 30 Oct 2020 11:57:16 -0400
From:   Zi Yan <zi.yan@...t.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:     Yang Shi <shy828301@...il.com>, Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Zi Yan <ziy@...dia.com>
Subject: [PATCH v2 2/2] mm/compaction: stop isolation if too many pages are isolated and we have pages to migrate.

From: Zi Yan <ziy@...dia.com>

In isolate_migratepages_block, if we have too many isolated pages and
nr_migratepages is not zero, we should try to migrate what we have
without wasting time on isolating.

Fixes: 1da2f328fa64 (“mm,thp,compaction,cma: allow THP migration for CMA allocations”)
Suggested-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Zi Yan <ziy@...dia.com>
Cc: <stable@...r.kernel.org>
---
 mm/compaction.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index 3e834ac402f1..4d237a7c3830 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -817,6 +817,10 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 	 * delay for some time until fewer pages are isolated
 	 */
 	while (unlikely(too_many_isolated(pgdat))) {
+		/* stop isolation if there are still pages not migrated */
+		if (cc->nr_migratepages)
+			return 0;
+
 		/* async migration should just abort */
 		if (cc->mode == MIGRATE_ASYNC)
 			return 0;
-- 
2.28.0