From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935365AbaKNPHM (ORCPT ); Fri, 14 Nov 2014 10:07:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57098 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934535AbaKNPHK (ORCPT ); Fri, 14 Nov 2014 10:07:10 -0500 Message-ID: <54661A8C.5050806@redhat.com> Date: Fri, 14 Nov 2014 10:06:52 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 MIME-Version: 1.0 To: Michal Hocko , linux-mm@kvack.org CC: Andrew Morton , Hugh Dickins , Michel Lespinasse , Andrea Argangeli , Linus Torvalds , Vlastimil Babka , Daniel Forrest , LKML Subject: Re: anon_vma accumulating for certain load still not addressed References: <20141114130822.GC22857@dhcp22.suse.cz> In-Reply-To: <20141114130822.GC22857@dhcp22.suse.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/14/2014 08:08 AM, Michal Hocko wrote: > Hi, > back in 2012 [1] there was a discussion about a forking load which > accumulates anon_vmas. There was a trivial test case which triggers this > and can potentially deplete the memory by local user. > > We have a report for an older enterprise distribution where nsd is > suffering from this issue most probably (I haven't debugged it throughly > but accumulating anon_vma structs over time sounds like a good enough > fit) and has to be restarted after some time to release the accumulated > anon_vma objects. > > There was a patch which tried to work around the issue [2] but I do not > see any follow ups nor any indication that the issue would be addressed > in other way. > > The test program from [1] was running for around 39 mins on my laptop > and here is the result: > > $ date +%s; grep anon_vma /proc/slabinfo > 1415960225 > anon_vma 11664 11900 160 25 1 : tunables 0 0 0 : slabdata 476 476 0 > > $ ./a # The reproducer > > $ date +%s; grep anon_vma /proc/slabinfo > 1415962592 > anon_vma 34875 34875 160 25 1 : tunables 0 0 0 : slabdata 1395 1395 0 > > $ killall a > $ date +%s; grep anon_vma /proc/slabinfo > 1415962607 > anon_vma 11277 12175 160 25 1 : tunables 0 0 0 : slabdata 487 487 0 > > So we have accumulated 23211 objects over that time period before the > offender was killed which released all of them. > > The proposed workaround is kind of ugly but do people have a better idea > than reference counting? If not should we merge it? I believe we should just merge that patch. I have not seen any better ideas come by. The comment should probably be fixed to reflect the chain length of 5 though :)