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=-5.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 2F6B0C43387 for ; Thu, 3 Jan 2019 19:23:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F3FA121872 for ; Thu, 3 Jan 2019 19:23:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546543424; bh=xvncojBUe26ihPmTV38uurQuIpybNKstjbPx4KplcEI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=xGG8jHI1ZgJarfzAP7MQB8qMqWu1zHfx0UuGtNN77VO8MQRJFB64B3/Vw4YbIgtXZ ttBIPfimlBpU5dC4ln7J0Uc5b1BQLjHOK5r/T6EBLFNTnB1KiVEm3k5IaMyGPIFZeq dvZmpyDahVnE3fTuXbf1js/41BPs5+c0s1goWnwE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727129AbfACTXn (ORCPT ); Thu, 3 Jan 2019 14:23:43 -0500 Received: from mx2.suse.de ([195.135.220.15]:43646 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727099AbfACTXm (ORCPT ); Thu, 3 Jan 2019 14:23:42 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id D3600AFA5; Thu, 3 Jan 2019 19:23:40 +0000 (UTC) Date: Thu, 3 Jan 2019 20:23:39 +0100 From: Michal Hocko To: Yang Shi Cc: hannes@cmpxchg.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/3] mm: memcontrol: delayed force empty Message-ID: <20190103192339.GA31793@dhcp22.suse.cz> References: <1546459533-36247-1-git-send-email-yang.shi@linux.alibaba.com> <20190103101215.GH31793@dhcp22.suse.cz> <20190103181329.GW31793@dhcp22.suse.cz> <6f43e926-3bb5-20d1-2e39-1d30bf7ad375@linux.alibaba.com> <20190103185333.GX31793@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 03-01-19 11:10:00, Yang Shi wrote: > > > On 1/3/19 10:53 AM, Michal Hocko wrote: > > On Thu 03-01-19 10:40:54, Yang Shi wrote: > > > > > > On 1/3/19 10:13 AM, Michal Hocko wrote: [...] > > > > Is there any reason for your scripts to be strictly sequential here? In > > > > other words why cannot you offload those expensive operations to a > > > > detached context in _userspace_? > > > I would say it has not to be strictly sequential. The above script is just > > > an example to illustrate the pattern. But, sometimes it may hit such pattern > > > due to the complicated cluster scheduling and container scheduling in the > > > production environment, for example the creation process might be scheduled > > > to the same CPU which is doing force_empty. I have to say I don't know too > > > much about the internals of the container scheduling. > > In that case I do not see a strong reason to implement the offloding > > into the kernel. It is an additional code and semantic to maintain. > > Yes, it does introduce some additional code and semantic, but IMHO, it is > quite simple and very straight forward, isn't it? Just utilize the existing > css offline worker. And, that a couple of lines of code do improve some > throughput issues for some real usecases. I do not really care it is few LOC. It is more important that it is conflating force_empty into offlining logic. There was a good reason to remove reparenting/emptying the memcg during the offline. Considering that you can offload force_empty from userspace trivially then I do not see any reason to implement it in the kernel. > > I think it is more important to discuss whether we want to introduce > > force_empty in cgroup v2. > > We would prefer have it in v2 as well. Then bring this up in a separate email thread please. -- Michal Hocko SUSE Labs