From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D9EEC04EB9 for ; Tue, 4 Dec 2018 02:53:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 554572087F for ; Tue, 4 Dec 2018 02:53:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 554572087F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726007AbeLDCxs (ORCPT ); Mon, 3 Dec 2018 21:53:48 -0500 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:38707 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725971AbeLDCxr (ORCPT ); Mon, 3 Dec 2018 21:53:47 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07417;MF=xlpang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0TEowmpW_1543892012; Received: from xunleideMacBook-Pro.local(mailfrom:xlpang@linux.alibaba.com fp:SMTPD_---0TEowmpW_1543892012) by smtp.aliyun-inc.com(127.0.0.1); Tue, 04 Dec 2018 10:53:33 +0800 Reply-To: xlpang@linux.alibaba.com Subject: Re: [PATCH 3/3] mm/memcg: Avoid reclaiming below hard protection To: Michal Hocko Cc: Roman Gushchin , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20181203080119.18989-1-xlpang@linux.alibaba.com> <20181203080119.18989-3-xlpang@linux.alibaba.com> <20181203115736.GQ31738@dhcp22.suse.cz> From: Xunlei Pang Message-ID: <8d8e860d-f9a4-6708-ccab-d47180f0ad0a@linux.alibaba.com> Date: Tue, 4 Dec 2018 10:53:32 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:60.0) Gecko/20100101 Thunderbird/60.3.2 MIME-Version: 1.0 In-Reply-To: <20181203115736.GQ31738@dhcp22.suse.cz> Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/12/3 PM 7:57, Michal Hocko wrote: > On Mon 03-12-18 16:01:19, Xunlei Pang wrote: >> When memcgs get reclaimed after its usage exceeds min, some >> usages below the min may also be reclaimed in the current >> implementation, the amount is considerably large during kswapd >> reclaim according to my ftrace results. > > And here again. Describe the setup and the behavior please? > step 1 mkdir -p /sys/fs/cgroup/memory/online cd /sys/fs/cgroup/memory/online echo 512M > memory.max echo 409600000 > memory.min echo $$ > tasks dd if=/dev/sda of=/dev/null while true; do sleep 1; cat memory.current ; cat memory.min; done step 2 create global memory pressure by allocating annoymous and cached pages to constantly trigger kswap: dd if=/dev/sdb of=/dev/null step 3 Then observe "online" groups, hundreds of kbytes a little over memory.min can cause tens of MiB to be reclaimed by kswapd. Here is one of test results I got: cat memory.current; cat memory.min; echo; 409485312 // current 409600000 // min 385052672 // See current got over reclaimed for 23MB 409600000 // min Its corresponding ftrace output I monitored: kswapd_0-281 [000] .... 304.706632: shrink_node_memcg: min_excess=24, nr_reclaimed=6013, sc->nr_to_reclaim=1499997, exceeds 5989pages