linux-kernel - [RFC PATCH 19/26] mm: compaction: drop redundant watermark check in compaction_zonelist

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Date:   Tue, 18 Apr 2023 15:13:06 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     linux-mm@...ck.org
Cc:     Kaiyang Zhao <kaiyang2@...cmu.edu>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: [RFC PATCH 19/26] mm: compaction: drop redundant watermark check in compaction_zonelist_suitable()

should_compact_retry() is called after direct reclaim and compaction
have failed to produce a page, to check if there is still enough
compactable memory to warrant continuing. If there aren't, one last
attempt at the freelists happens in __alloc_pages_may_oom(). The
watermark check in should_compact_retry() is not necessary. Kill it.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/compaction.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 0aa2a0a192dc..52103545d58c 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2263,13 +2263,6 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
 				ac->highest_zoneidx, ac->nodemask) {
 		unsigned long available;
-		unsigned long watermark;
-
-		/* Allocation can already succeed, nothing to do */
-		watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
-		if (zone_watermark_ok(zone, order, watermark,
-				      ac->highest_zoneidx, alloc_flags))
-			continue;
 
 		available = zone_page_state_snapshot(zone, NR_FREE_MOVABLE);
 		available += zone_page_state_snapshot(zone, NR_FREE_CMA_PAGES);
-- 
2.39.2