linux-kernel - [PATCH] mm: forbid lumpy-reclaim in shrink_active

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Date:	Mon, 19 Mar 2012 13:18:21 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Cc:	Rik van Riel <riel@...hat.com>, Hugh Dickins <hughd@...gle.com>,
	Minchan Kim <minchan@...nel.org>, Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <jweiner@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: [PATCH] mm: forbid lumpy-reclaim in shrink_active_list()

This patch reset reclaim mode in shrink_active_list() to RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC.
(sync/async sign is used only in shrink_page_list and does not affect shrink_active_list)

Currenly shrink_active_list() sometimes works in lumpy-reclaim mode,
if RECLAIM_MODE_LUMPYRECLAIM left over from earlier shrink_inactive_list().
Meanwhile, in age_active_anon() sc->reclaim_mode is totally zero.
So, current behavior is too complex and confusing, all this looks like bug.

In general, shrink_active_list() populate inactive list for next shrink_inactive_list().
Lumpy shring_inactive_list() isolate pages around choosen one from both active and
inactive lists. So, there no reasons for lumpy-isolation in shrink_active_list()

Proposed-by: Hugh Dickins <hughd@...gle.com>
Link: https://lkml.org/lkml/2012/3/15/583
Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
---
 mm/vmscan.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 57d8ef6..ae83ca3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1690,6 +1690,8 @@ static void shrink_active_list(unsigned long nr_to_scan,

 	lru_add_drain();

+	reset_reclaim_mode(sc);
+
 	if (!sc->may_unmap)
 		isolate_mode |= ISOLATE_UNMAPPED;
 	if (!sc->may_writepage)

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