From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752442AbeDETAS (ORCPT ); Thu, 5 Apr 2018 15:00:18 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:42152 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752313AbeDETAN (ORCPT ); Thu, 5 Apr 2018 15:00:13 -0400 From: Roman Gushchin To: CC: Roman Gushchin , Andrew Morton , Johannes Weiner , Michal Hocko , Vladimir Davydov , Tejun Heo , , , , Subject: [PATCH v3 4/4] mm/docs: describe memory.low refinements Date: Thu, 5 Apr 2018 19:59:21 +0100 Message-ID: <20180405185921.4942-4-guro@fb.com> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180405185921.4942-1-guro@fb.com> References: <20180405185921.4942-1-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [2620:10d:c092:200::1:c820] X-ClientProxiedBy: DB6PR0601CA0040.eurprd06.prod.outlook.com (2603:10a6:4:17::26) To CO1PR15MB1078.namprd15.prod.outlook.com (2a01:111:e400:7b66::8) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 3fcb1d12-cdf0-4352-f67b-08d59b276ad8 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(5600026)(4604075)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7153060)(7193020);SRVR:CO1PR15MB1078; 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Signed-off-by: Roman Gushchin Cc: Andrew Morton Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Cc: Tejun Heo Cc: kernel-team@fb.com Cc: linux-mm@kvack.org Cc: cgroups@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-doc@vger.kernel.org --- Documentation/cgroup-v2.txt | 28 +++++++++++++--------------- 1 file changed, 13 insertions(+), 15 deletions(-) diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt index f728e55602b2..7ee462b8a6ac 100644 --- a/Documentation/cgroup-v2.txt +++ b/Documentation/cgroup-v2.txt @@ -1006,10 +1006,17 @@ PAGE_SIZE multiple when read back. A read-write single value file which exists on non-root cgroups. The default is "0". - Best-effort memory protection. If the memory usages of a - cgroup and all its ancestors are below their low boundaries, - the cgroup's memory won't be reclaimed unless memory can be - reclaimed from unprotected cgroups. + Best-effort memory protection. If the memory usage of a + cgroup is within its effective low boundary, the cgroup's + memory won't be reclaimed unless memory can be reclaimed + from unprotected cgroups. + + Effective low boundary is limited by memory.low values of + all ancestor cgroups. If there is memory.low overcommitment + (child cgroup or cgroups are requiring more protected memory, + than parent will allow), then each child cgroup will get + the part of parent's protection proportional to the its + actual memory usage below memory.low. Putting more memory than generally available under this protection is discouraged. @@ -2008,17 +2015,8 @@ system performance due to overreclaim, to the point where the feature becomes self-defeating. The memory.low boundary on the other hand is a top-down allocated -reserve. A cgroup enjoys reclaim protection when it and all its -ancestors are below their low boundaries, which makes delegation of -subtrees possible. Secondly, new cgroups have no reserve per default -and in the common case most cgroups are eligible for the preferred -reclaim pass. This allows the new low boundary to be efficiently -implemented with just a minor addition to the generic reclaim code, -without the need for out-of-band data structures and reclaim passes. -Because the generic reclaim code considers all cgroups except for the -ones running low in the preferred first reclaim pass, overreclaim of -individual groups is eliminated as well, resulting in much better -overall workload performance. +reserve. A cgroup enjoys reclaim protection when it's within its low, +which makes delegation of subtrees possible. The original high boundary, the hard limit, is defined as a strict limit that can not budge, even if the OOM killer has to be called. -- 2.14.3