From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751680AbdG0HGO (ORCPT ); Thu, 27 Jul 2017 03:06:14 -0400 Received: from mx2.suse.de ([195.135.220.15]:41935 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750765AbdG0HGN (ORCPT ); Thu, 27 Jul 2017 03:06:13 -0400 Date: Thu, 27 Jul 2017 09:06:08 +0200 From: Michal Hocko To: Andrew Morton Cc: Davidlohr Bueso , mingo@kernel.org, peterz@infradead.org, jack@suse.cz, torvalds@linux-foundation.org, kirill.shutemov@linux.intel.com, hch@infradead.org, ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net, linux-kernel@vger.kernel.org, Davidlohr Bueso , Johannes Weiner , Vladimir Davydov Subject: Re: [PATCH 16/17] mem/memcg: cache rightmost node Message-ID: <20170727070608.GF20970@dhcp22.suse.cz> References: <20170719014603.19029-1-dave@stgolabs.net> <20170719014603.19029-17-dave@stgolabs.net> <20170719075036.GA26779@dhcp22.suse.cz> <20170726140927.1408d4308795d3e3fdb082c4@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170726140927.1408d4308795d3e3fdb082c4@linux-foundation.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 26-07-17 14:09:27, Andrew Morton wrote: > On Wed, 19 Jul 2017 09:50:36 +0200 Michal Hocko wrote: > > > [CC Johannes and Vladimir - the whole series is > > http://lkml.kernel.org/r/20170719014603.19029-1-dave@stgolabs.net] > > > > On Tue 18-07-17 18:46:02, Davidlohr Bueso wrote: > > > Such that we can optimize __mem_cgroup_largest_soft_limit_node(). > > > The only overhead is the extra footprint for the cached pointer, > > > but this should not be an issue for mem_cgroup_tree_per_node. > > > > The soft limit reclaim and the associated tree manipulation is not worth > > touching/optimizing IMHO. We strongly discourage anybody configuring > > soft limit because of the way how it is implemented and disruptive. > > I'm inclined to merge this. Unless we plan to actually remove the code > "soon", this is not going to happen. It is a user visible interface so we will have to maintain it as long as cgroup v1 interface is available > I think it's best to continue to improve it. Improving > performance may never matter to anyone, but there is benefit in keeping > up to date with the current interfaces and best practices. Well, I am not opposing the change I just think it is not worth bothering. Soft limit reclaim tends to be so expensive (direct limit down to the soft limit) that a tiny otimization has hard times to help. -- Michal Hocko SUSE Labs