Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750975AbaKYPAK (ORCPT ); Tue, 25 Nov 2014 10:00:10 -0500 Received: from cantor2.suse.de ([195.135.220.15]:42899 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750860AbaKYPAI (ORCPT ); Tue, 25 Nov 2014 10:00:08 -0500 Date: Tue, 25 Nov 2014 16:00:06 +0100 From: Michal Hocko To: Konstantin Khlebnikov Cc: Rik van Riel , Michel Lespinasse , Vlastimil Babka , Andrew Morton , Hugh Dickins , Andrea Arcangeli , Linux Kernel Mailing List , "linux-mm@kvack.org" , Tim Hartrick Subject: Re: [PATCH] Repeated fork() causes SLAB to grow without bound Message-ID: <20141125150006.GB4415@dhcp22.suse.cz> References: <546CC0CD.40906@suse.cz> <546DFFA1.4030700@redhat.com> <20141125105953.GC4607@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Tue 25-11-14 16:13:16, Konstantin Khlebnikov wrote: > On Tue, Nov 25, 2014 at 1:59 PM, Michal Hocko wrote: > > On Mon 24-11-14 11:09:40, Konstantin Khlebnikov wrote: > >> On Thu, Nov 20, 2014 at 6:03 PM, Konstantin Khlebnikov wrote: > >> > On Thu, Nov 20, 2014 at 5:50 PM, Rik van Riel wrote: > >> >> -----BEGIN PGP SIGNED MESSAGE----- > >> >> Hash: SHA1 > >> >> > >> >> On 11/20/2014 09:42 AM, Konstantin Khlebnikov wrote: > >> >> > >> >>> I'm thinking about limitation for reusing anon_vmas which might > >> >>> increase performance without breaking asymptotic estimation of > >> >>> count anon_vma in the worst case. For example this heuristic: allow > >> >>> to reuse only anon_vma with single direct descendant. It seems > >> >>> there will be arount up to two times more anon_vmas but > >> >>> false-aliasing must be much lower. > >> > >> Done. RFC patch in attachment. > > > > This is triggering BUG_ON(anon_vma->degree); in unlink_anon_vmas. I have > > applied the patch on top of 3.18.0-rc6. > > It seems I've screwed up with counter if anon_vma is merged in anon_vma_prepare. > Increment must be in the next if block: > > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -182,8 +182,6 @@ int anon_vma_prepare(struct vm_area_struct *vma) > if (unlikely(!anon_vma)) > goto out_enomem_free_avc; > allocated = anon_vma; > - /* Bump degree, root anon_vma is its own parent. */ > - anon_vma->degree++; > } > > anon_vma_lock_write(anon_vma); > @@ -192,6 +190,7 @@ int anon_vma_prepare(struct vm_area_struct *vma) > if (likely(!vma->anon_vma)) { > vma->anon_vma = anon_vma; > anon_vma_chain_link(vma, avc, anon_vma); > + anon_vma->degree++; > allocated = NULL; > avc = NULL; > } > > I've tested it with trinity but probably isn't long enough. OK, this has passed few runs with the original reproducer: $ date +%s; grep anon_vma /proc/slabinfo; $ ./vma_chain_repro $ sleep 1h $ date +%s; grep anon_vma /proc/slabinfo $ killall vma_chain_repro $ date +%s; grep anon_vma /proc/slabinfo 1416923468 anon_vma 11523 11523 176 23 1 : tunables 0 0 0 : slabdata 501 501 0 1416927070 anon_vma 11477 11477 176 23 1 : tunables 0 0 0 : slabdata 499 499 0 1416927070 anon_vma 11127 11431 176 23 1 : tunables 0 0 0 : slabdata 497 497 0 anon_vmas do not seem to leak anymore. I have forwarded the patch to the customer who was complaining about NSD but I guess it will take some time to get the confirmation. Anyway thanks a lot for your help and feel free to add Tested-by: Michal Hocko I have yet to look deeper into the code to give you my Reviewed-by. -- Michal Hocko SUSE Labs -- 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/