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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 A8371C433E2 for ; Wed, 9 Sep 2020 11:45:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 705A421D43 for ; Wed, 9 Sep 2020 11:45:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729449AbgIILpX (ORCPT ); Wed, 9 Sep 2020 07:45:23 -0400 Received: from mx2.suse.de ([195.135.220.15]:36500 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726293AbgIILmO (ORCPT ); Wed, 9 Sep 2020 07:42:14 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0C6D4B732; Wed, 9 Sep 2020 11:40:59 +0000 (UTC) Date: Wed, 9 Sep 2020 13:40:57 +0200 From: Michal Hocko To: Aaron Lu Cc: Daniel Jordan , Alex Shi , Hugh Dickins , Andrew Morton , mgorman@techsingularity.net, tj@kernel.org, khlebnikov@yandex-team.ru, willy@infradead.org, hannes@cmpxchg.org, lkp@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, shakeelb@google.com, iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com, kirill@shutemov.name, alexander.duyck@gmail.com, rong.a.chen@intel.com, vdavydov.dev@gmail.com, shy828301@gmail.com Subject: Re: [PATCH v18 00/32] per memcg lru_lock Message-ID: <20200909114057.GH7348@dhcp22.suse.cz> References: <1598273705-69124-1-git-send-email-alex.shi@linux.alibaba.com> <20200824114204.cc796ca182db95809dd70a47@linux-foundation.org> <20200825015627.3c3pnwauqznnp3gc@ca-dmjordan1.us.oracle.com> <20200826011946.spknwjt44d2szrdo@ca-dmjordan1.us.oracle.com> <01ed6e45-3853-dcba-61cb-b429a49a7572@linux.alibaba.com> <20200828014022.y5xju6weysqpzxd2@ca-dmjordan1.us.oracle.com> <20200909024432.GA9736@desktop-ziqianlu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200909024432.GA9736@desktop-ziqianlu> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 09-09-20 10:44:32, Aaron Lu wrote: > On Thu, Aug 27, 2020 at 09:40:22PM -0400, Daniel Jordan wrote: > > I went back to your v1 post to see what motivated you originally, and you had > > some results from aim9 but nothing about where this reared its head in the > > first place. How did you discover the bottleneck? I'm just curious about how > > lru_lock hurts in practice. > > I think making lru_lock per-memcg helps in colocated environment: some > workloads are of high priority while some workloads are of low priority. > > For these low priority workloads, we may even want to use some swap for > it to save memory and this can cause frequent alloc/reclaim, depending > on its workingset etc. and these alloc/reclaim need to hold the global > lru lock and zone lock. And then when the high priority workloads do > page fault, their performance can be adversely affected and that is not > acceptible since these high priority workloads normally have strict SLA > requirement. While this all sounds reasonably. We are lacking _any_ numbers to actually make that a solid argumentation rather than hand waving. Having something solid is absolutely necessary for a big change like this. -- Michal Hocko SUSE Labs