Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933638AbdCLKZZ (ORCPT ); Sun, 12 Mar 2017 06:25:25 -0400 Received: from SMTPBG354.QQ.COM ([59.37.110.87]:60331 "EHLO smtpbg.qq.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755667AbdCLKZR (ORCPT ); Sun, 12 Mar 2017 06:25:17 -0400 X-Greylist: delayed 475 seconds by postgrey-1.27 at vger.kernel.org; Sun, 12 Mar 2017 06:25:16 EDT X-QQ-Spam: true X-QQ-mid: esmtp31t1489313706t2aprgwjb X-QQ-SSF: 01000000000000202G100400000000V Subject: Re: [PATCH v2 RFC] mm/vmscan: more restrictive condition for retry in do_try_to_free_pages To: Shakeel Butt References: <1489240264-3290-1-git-send-email-ysxie@foxmail.com> Cc: Andrew Morton , Johannes Weiner , Mel Gorman , Vlastimil Babka , Michal Hocko , riel@redhat.com, Linux MM , LKML , xieyisheng1@huawei.com, guohanjun@huawei.com, Xishi Qiu From: Yisheng Xie Message-ID: <58C51FA9.4000705@foxmail.com> Date: Sun, 12 Mar 2017 18:15:05 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-QQ-SENDSIZE: 520 Feedback-ID: esmtp:foxmail.com:bgweb:bgweb154 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1847 Lines: 46 hi, Shakeel, On 03/12/2017 01:52 AM, Shakeel Butt wrote: > On Sat, Mar 11, 2017 at 5:51 AM, Yisheng Xie wrote: >> From: Yisheng Xie >> >> When we 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, 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 time costly and useless retrying, add a stub function >> may_thrash and return true when memcg is disabled or on legacy >> hierarchy. >> >> Signed-off-by: Yisheng Xie >> Suggested-by: Shakeel Butt >> --- >> >> return 1; >> >> /* Untapped cgroup reserves? Don't OOM, retry. */ >> - if (!sc->may_thrash) { >> + if (!may_thrash(sc)) { > Thanks Yisheng. The name of the function may_thrash() is confusing in > the sense that it is returning exactly the opposite of what its name > implies. Right. > How about reversing the condition of may_thrash() function > and change the scan_control's field may_thrash to thrashed? hmm, maybe I can change the may_thrash() function to mem_cgroup_thrashed(). For, if change the scan_control's may_thrash to thrashed, it may also looks confusing in shrink_node, and it will be like: if (mem_cgroup_low(root, memcg)) { if (!sc->thrashed) -----> looks confuse here? continue; mem_cgroup_events(memcg, MEMCG_LOW, 1); } Thanks Yisheng Xie @