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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,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 047CBC31E49 for ; Sun, 16 Jun 2019 04:07:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA69E216C8 for ; Sun, 16 Jun 2019 04:07:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725880AbfFPEHs (ORCPT ); Sun, 16 Jun 2019 00:07:48 -0400 Received: from out30-45.freemail.mail.aliyun.com ([115.124.30.45]:58833 "EHLO out30-45.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725773AbfFPEHs (ORCPT ); Sun, 16 Jun 2019 00:07:48 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R501e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07486;MF=xlpang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0TUHzmZd_1560658064; Received: from xunleideMacBook-Pro.local(mailfrom:xlpang@linux.alibaba.com fp:SMTPD_---0TUHzmZd_1560658064) by smtp.aliyun-inc.com(127.0.0.1); Sun, 16 Jun 2019 12:07:45 +0800 Reply-To: xlpang@linux.alibaba.com Subject: Re: [PATCH] psi: Don't account force reclaim as memory pressure To: Chris Down Cc: Roman Gushchin , Michal Hocko , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20190615120644.26743-1-xlpang@linux.alibaba.com> <20190615155831.GA1307@chrisdown.name> From: Xunlei Pang Message-ID: <130aca9c-4d73-49ed-e78a-534ce2100ff8@linux.alibaba.com> Date: Sun, 16 Jun 2019 12:07:44 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <20190615155831.GA1307@chrisdown.name> 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 Hi Chris, On 2019/6/15 PM 11:58, Chris Down wrote: > Hi Xunlei, > > Xunlei Pang writes: >> There're several cases like resize and force_empty that don't >> need to account to psi, otherwise is misleading. > > I'm afraid I'm quite confused by this patch. Why do you think accounting > for force reclaim in PSI is misleading? I completely expect that force > reclaim should still be accounted for as memory pressure, can you > present some reason why it shouldn't be? We expect psi stands for negative factors to applications which affect their response time, but force reclaims are behaviours triggered on purpose like "/proc/sys/vm/drop_caches", not the real negative pressure. e.g. my module force reclaims the dead memcgs, there's no application attached to it, and its memory(page caches) is usually useless, force reclaiming them doesn't mean the system or parent memcg is under memory pressure, while actually the whole system or the parent memcg has plenty of free memory. If the force reclaim causes further memory pressure like hot page cache miss, then the workingset refault psi will catch that.