linux-kernel - [PATCH] mm: compact: remove watermark check at compact suitable

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Message-ID: <1463973617-10599-1-git-send-email-puck.chen@hisilicon.com>
Date:	Mon, 23 May 2016 11:20:17 +0800
From:	Chen Feng <puck.chen@...ilicon.com>
To:	<puck.chen@...ilicon.com>, <akpm@...ux-foundation.org>,
	<vbabka@...e.cz>, <iamjoonsoo.kim@....com>, <mina86@...a86.com>,
	<rientjes@...gle.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
CC:	<xuyiping@...ilicon.com>, <suzhuangluan@...ilicon.com>,
	<dan.zhao@...ilicon.com>, <qijiwen@...ilicon.com>,
	<oliver.fu@...ilicon.com>, <puck.chen@...mail.com>
Subject: [PATCH] mm: compact: remove watermark check at compact suitable

There are two paths calling this function.
For direct compact, there is no need to check the zone watermark here.
For kswapd wakeup kcompactd, since there is a reclaim before this.
It makes sense to do compact even the watermark is ok at this time.

Signed-off-by: Chen Feng <puck.chen@...ilicon.com>
---
 mm/compaction.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 8fa2540..cb322df 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1260,13 +1260,6 @@ static unsigned long __compaction_suitable(struct zone *zone, int order,
 		return COMPACT_CONTINUE;
 
 	watermark = low_wmark_pages(zone);
-	/*
-	 * If watermarks for high-order allocation are already met, there
-	 * should be no need for compaction at all.
-	 */
-	if (zone_watermark_ok(zone, order, watermark, classzone_idx,
-								alloc_flags))
-		return COMPACT_PARTIAL;
 
 	/*
 	 * Watermarks for order-0 must be met for compaction. Note the 2UL.
-- 
1.9.1