Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753835AbdCOLn4 (ORCPT ); Wed, 15 Mar 2017 07:43:56 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:3882 "EHLO dggrg02-dlp.huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1753173AbdCOLnY (ORCPT ); Wed, 15 Mar 2017 07:43:24 -0400 From: Yisheng Xie To: , , , , , , CC: , , , Subject: [PATCH v4] mm/vmscan: more restrictive condition for retry in do_try_to_free_pages Date: Wed, 15 Mar 2017 19:36:48 +0800 Message-ID: <1489577808-19228-1-git-send-email-xieyisheng1@huawei.com> X-Mailer: git-send-email 1.7.12.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.102.37] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.58C928C5.0398,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 8bc40028758803d35a3878d1c39dd178 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2680 Lines: 78 By reviewing code, I find that when enter do_try_to_free_pages, the may_thrash is always clear, and it will retry shrink zones to tap cgroup's reserves memory by setting may_thrash when the former shrink_zones reclaim nothing. However, when memcg is disabled or on legacy hierarchy, or there do not have any memcg protected by low limit, it should not do this useless retry at all, for we do not have any cgroup's reserves memory to tap, and we have already done hard work but made no progress. To avoid this unneeded retrying, add a new field in scan_control named memcg_low_protection, set it if there is any memcg protected by low limit and only do the retry when memcg_low_protection is set while may_thrash is clear. Signed-off-by: Yisheng Xie Suggested-by: Michal Hocko Suggested-by: Shakeel Butt Reviewed-by: Shakeel Butt --- v4: - add a new field in scan_control named memcg_low_protection to check whether there have any memcg protected by low limit. - Michal v3: - rename function may_thrash() to mem_cgroup_thrashed() to avoid confusing. v2: - more restrictive condition for retry of shrink_zones (restricting cgroup_disabled=memory boot option and cgroup legacy hierarchy) - Shakeel - add a stub function may_thrash() to avoid compile error or warning. - rename subject from "donot retry shrink zones when memcg is disable" to "more restrictive condition for retry in do_try_to_free_pages" Any comment is more than welcome! Thanks Yisheng Xie mm/vmscan.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index bc8031e..c4fa3d3 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -100,6 +100,9 @@ struct scan_control { /* Can cgroups be reclaimed below their normal consumption range? */ unsigned int may_thrash:1; + /* Did we have any memcg protected by the low limit */ + unsigned int memcg_low_protection:1; + unsigned int hibernation_mode:1; /* One of the zones is ready for compaction */ @@ -2557,6 +2560,8 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc) unsigned long scanned; if (mem_cgroup_low(root, memcg)) { + sc->memcg_low_protection = 1; + if (!sc->may_thrash) continue; mem_cgroup_events(memcg, MEMCG_LOW, 1); @@ -2808,7 +2813,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, return 1; /* Untapped cgroup reserves? Don't OOM, retry. */ - if (!sc->may_thrash) { + if (sc->memcg_low_protection && !sc->may_thrash) { sc->priority = initial_priority; sc->may_thrash = 1; goto retry; -- 1.7.12.4