linux-kernel - [PATCH 3.16 199/233] swap: cond_resched in swap_cgroup

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Date:   Sat, 09 Sep 2017 22:47:15 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Vladimir Davydov" <vdavydov.dev@...il.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Yu Zhao" <yuzhao@...gle.com>, "Michal Hocko" <mhocko@...e.com>
Subject: [PATCH 3.16 199/233] swap: cond_resched in swap_cgroup_prepare()

3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Yu Zhao <yuzhao@...gle.com>

commit ef70762948dde012146926720b70e79736336764 upstream.

I saw need_resched() warnings when swapping on large swapfile (TBs)
because continuously allocating many pages in swap_cgroup_prepare() took
too long.

We already cond_resched when freeing page in swap_cgroup_swapoff().  Do
the same for the page allocation.

Link: http://lkml.kernel.org/r/20170604200109.17606-1-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@...gle.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Acked-by: Vladimir Davydov <vdavydov.dev@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 mm/page_cgroup.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -368,6 +368,9 @@ static int swap_cgroup_prepare(int type)
 		if (!page)
 			goto not_enough_page;
 		ctrl->map[idx] = page;
+
+		if (!(idx % SWAP_CLUSTER_MAX))
+			cond_resched();
 	}
 	return 0;
 not_enough_page: