Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753519AbbHCNwt (ORCPT ); Mon, 3 Aug 2015 09:52:49 -0400 Received: from relay.parallels.com ([195.214.232.42]:59349 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753081AbbHCNws (ORCPT ); Mon, 3 Aug 2015 09:52:48 -0400 Date: Mon, 3 Aug 2015 16:52:29 +0300 From: Vladimir Davydov To: Johannes Weiner CC: Andrew Morton , Michal Hocko , Minchan Kim , Rik van Riel , Mel Gorman , , Subject: Re: [PATCH 2/3] mm: make workingset detection logic memcg aware Message-ID: <20150803135229.GA11971@esperanza> References: <9662034e14549b9e1445684f674063ce8b092cb0.1438599199.git.vdavydov@parallels.com> <20150803132358.GA18399@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20150803132358.GA18399@cmpxchg.org> X-ClientProxiedBy: US-EXCH.sw.swsoft.com (10.255.249.47) 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: 1978 Lines: 44 On Mon, Aug 03, 2015 at 09:23:58AM -0400, Johannes Weiner wrote: > On Mon, Aug 03, 2015 at 03:04:22PM +0300, Vladimir Davydov wrote: > > @@ -179,8 +180,9 @@ static void unpack_shadow(void *shadow, > > eviction = entry; > > > > *zone = NODE_DATA(nid)->node_zones + zid; > > + *lruvec = mem_cgroup_page_lruvec(page, *zone); > > > > - refault = atomic_long_read(&(*zone)->inactive_age); > > + refault = atomic_long_read(&(*lruvec)->inactive_age); > > mask = ~0UL >> (NODES_SHIFT + ZONES_SHIFT + > > RADIX_TREE_EXCEPTIONAL_SHIFT); > > /* > > You can not compare an eviction shadow entry from one lruvec with the > inactive age of another lruvec. The inactive ages are not related and > might differ significantly: memcgs are created ad hoc, memory hotplug, > page allocator fairness drift. In those cases the result will be pure > noise. That's true. If a page is evicted in one cgroup and then refaulted in another, the activation will be random. However, is it a frequent event when a page used by and evicted from one cgroup is refaulted in another? If there is no active file sharing (is it common?), this should only happen to code pages, but those will most likely end up in the cgroup that has the greatest limit, so they shouldn't be evicted and refaulted frequently. So the question is can we tolerate some noise here? > > As much as I would like to see a simpler way, I am pessimistic that > there is a way around storing memcg ids in the shadow entries. On 32 bit there is too little space for storing memcg id. We can shift the distance so that it would fit and still contain something meaningful though, but that would take much more code, so I'm trying to try the simplest way first. 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/