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From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Mel Gorman <mgorman@techsingularity.net>,
        Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@suse.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH 5/5] mm: compaction: drop redundant watermark check in compaction_zonelist_suitable()
Date:   Fri, 19 May 2023 14:39:59 +0200
Message-Id: <20230519123959.77335-6-hannes@cmpxchg.org>
In-Reply-To: <20230519123959.77335-1-hannes@cmpxchg.org>
References: <20230519123959.77335-1-hannes@cmpxchg.org>
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The watermark check in compaction_zonelist_suitable(), called from
should_compact_retry(), is sandwiched between two watermark checks
already: before, there are freelist attempts as part of direct reclaim
and direct compaction; after, there is a last-minute freelist attempt
in __alloc_pages_may_oom().

The check in compaction_zonelist_suitable() isn't necessary. Kill it.

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

diff --git a/mm/compaction.c b/mm/compaction.c
index 83ecbc829c62..40ce4e6dd17e 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2291,13 +2291,6 @@ 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;
 
 		/*
 		 * Do not consider all the reclaimable memory because we do not
-- 
2.40.0