linux-kernel - [RFC] mm:do recheck for freeable page in reclaim path

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Message-ID: <35FD53F367049845BC99AC72306C23D10458D6173C0C@CNBJMBX05.corpusers.net>
Date:	Wed, 11 Mar 2015 17:47:28 +0800
From:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
To:	'Minchan Kim' <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Shaohua Li <shli@...nel.org>
Subject: [RFC] mm:do recheck for freeable page in reclaim path

In reclaim path, if encounter a freeable page,
the try_to_unmap may fail, because the page's pte is
dirty, we can recheck this page as normal non-freeable page,
this means we can swap out this page into swap partition.

Signed-off-by: Yalin Wang <yalin.wang@...ymobile.com>
---
 mm/vmscan.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 260c413..9930850 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1000,6 +1000,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			}
 		}
 
+recheck:
 		if (!force_reclaim)
 			references = page_check_references(page, sc,
 							&freeable);
@@ -1045,6 +1046,10 @@ unmap:
 			switch (try_to_unmap(page,
 				freeable ? TTU_FREE : ttu_flags)) {
 			case SWAP_FAIL:
+				if (freeable) {
+					freeable = false;
+					goto recheck;
+				}
 				goto activate_locked;
 			case SWAP_AGAIN:
 				goto keep_locked;
-- 
2.2.2
--
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