Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932818AbbHHNFU (ORCPT ); Sat, 8 Aug 2015 09:05:20 -0400 Received: from mx2.parallels.com ([199.115.105.18]:56385 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932707AbbHHNFR (ORCPT ); Sat, 8 Aug 2015 09:05:17 -0400 Date: Sat, 8 Aug 2015 16:05:01 +0300 From: Vladimir Davydov To: Kamezawa Hiroyuki CC: Andrew Morton , Johannes Weiner , Michal Hocko , Minchan Kim , Rik van Riel , Mel Gorman , , Subject: Re: [PATCH 0/3] Make workingset detection logic memcg aware Message-ID: <20150808130501.GA16760@esperanza> References: <55C16842.9040505@jp.fujitsu.com> <20150806085911.GL11971@esperanza> <55C40C08.8010706@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <55C40C08.8010706@jp.fujitsu.com> X-ClientProxiedBy: US-EXCH2.sw.swsoft.com (10.255.249.46) To US-EXCH2.sw.swsoft.com (10.255.249.46) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3473 Lines: 88 On Fri, Aug 07, 2015 at 10:38:16AM +0900, Kamezawa Hiroyuki wrote: > On 2015/08/06 17:59, Vladimir Davydov wrote: > >On Wed, Aug 05, 2015 at 10:34:58AM +0900, Kamezawa Hiroyuki wrote: > >>I wonder, rather than collecting more data, rough calculation can help the situation. > >>for example, > >> > >> (refault_disatance calculated in zone) * memcg_reclaim_ratio < memcg's active list > >> > >>If one of per-zone calc or per-memcg calc returns true, refault should be true. > >> > >>memcg_reclaim_ratio is the percentage of scan in a memcg against in a zone. > > > >This particular formula wouldn't work I'm afraid. If there are two > >isolated cgroups issuing local reclaim on the same zone, the refault > >distance needed for activation would be reduced by half for no apparent > >reason. > > Hmm, you mean activation in memcg means activation in global LRU, and it's not a > valid reason. Current implementation does have the same issue, right ? > > i.e. when a container has been hitting its limit for a while, and then, a file cache is > pushed out but came back soon, it can be easily activated. > > I'd like to confirm what you want to do. > > 1) avoid activating a file cache when it was kicked out because of memcg's local limit. No, that's not what I want. I want pages of the workingset to get activated on refault no matter if they were evicted on global memory pressure or due to hitting a memory cgroup limit. > 2) maintain acitve/inactive ratio in memcg properly as global LRU does. > 3) reclaim shadow entry at proper timing. > > All ? hmm. It seems that mixture of record of global memory pressure and of local memory > pressure is just wrong. What makes you think so? An example of misbehavior caused by this would be nice to have. > > Now, the record is > 　　　　 > 　　　　eviction | node | zone | 2bit. > > How about changing this as > > 0 |eviction | node | zone | 2bit > 1 |eviction | memcgid | 2bit > > Assume each memcg has an eviction counter, which ignoring node/zone. > i.e. memcg local reclaim happens against memcg not against zone. > > At page-in, > if (the 1st bit is 0) > compare eviction counter with zone's counter and activate the page if needed. > else if (the 1st bit is 1) > compare eviction counter with the memcg (if exists) Having a single counter per memcg won't scale with the number of NUMA nodes. > if (current memcg == recorded memcg && eviction distance is okay) > activate page. > else > inactivate > At page-out > if (global memory pressure) > record eviction id with using zone's counter. > else if (memcg local memory pressure) > record eviction id with memcg's counter. > I don't understand how this is supposed to work when a memory cgroup experiences both local and global pressure simultaneously. Also, what if a memory cgroup is protected by memory.low? Such a cgroup may have all its pages in the active list, because it is never scanned. This will affect the refault distance of other cgroups, making activations unpredictable. Thanks, Vladimir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/