Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933087AbbHIONJ (ORCPT ); Sun, 9 Aug 2015 10:13:09 -0400 Received: from mgwkm01.jp.fujitsu.com ([202.219.69.168]:47112 "EHLO mgwkm01.jp.fujitsu.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933066AbbHIONF (ORCPT ); Sun, 9 Aug 2015 10:13:05 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v2.3.2 X-SHieldMailCheckerPolicyVersion: FJ-ISEC-20150223 X-SHieldMailCheckerMailID: 07b9a52bfd4c4a6da8af4e739c24e9f9 Subject: Re: [PATCH 0/3] Make workingset detection logic memcg aware To: Vladimir Davydov References: <55C16842.9040505@jp.fujitsu.com> <20150806085911.GL11971@esperanza> <55C40C08.8010706@jp.fujitsu.com> <20150808130501.GA16760@esperanza> Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Minchan Kim , Rik van Riel , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org From: Kamezawa Hiroyuki Message-ID: <55C75FC9.2060803@jp.fujitsu.com> Date: Sun, 9 Aug 2015 23:12:25 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <20150808130501.GA16760@esperanza> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-MML: disable Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4738 Lines: 130 On 2015/08/08 22:05, Vladimir Davydov wrote: > 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. > Sure. >> 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. > By design, memcg's LRU aging logic is independent from global memory allocation/pressure. Assume there are 4 containers(using much page-cache) with 1GB limit on 4GB server, # contaienr A workingset=600M limit=1G (sleepy) # contaienr B workingset=300M limit=1G (work often) # container C workingset=500M limit=1G (work slowly) # container D workingset=1.2G limit=1G (work hard) container D can drive the zone's distance counter because of local memory reclaim. If active/inactive = 1:1, container D page can be activated. At kswapd(global reclaim) runs, all container's LRU will rotate. Possibility of refault in A, B, C is reduced by conainer D's counter updates. But yes, some _real_ test are required. >> >> 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. > It doesn't matter, we can use lazy counter like pcpu counter because it's not needed to be very accurate. >> 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. > I think updating global distance counter by local reclaim may update counter too much. Above is to avoid updating zone's counter and keep memcg's LRU active/inactive balanced. > 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. If LRU never scanned, all file caches tend to be in INACTIVE...it never refaults. > This will affect the refault distance of other cgroups, making > activations unpredictable. > Thanks, -Kame -- 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/