Message-ID: <546DFFA1.4030700@redhat.com>
Date: Thu, 20 Nov 2014 09:50:09 -0500
From: Rik van Riel <riel@redhat.com>
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To: Konstantin Khlebnikov <koct9i@gmail.com>,
        Michel Lespinasse <walken@google.com>
CC: Vlastimil Babka <vbabka@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Tim Hartrick <tim@edgecast.com>, Michal Hocko <mhocko@suse.cz>
Subject: Re: [PATCH] Repeated fork() causes SLAB to grow without bound
References: <502D42E5.7090403@redhat.com>	<alpine.LSU.2.00.1208200032450.24855@eggly.anvils>	<CANN689Ej7XLh8VKuaPrTttDrtDGQbXuYJgS2uKnZL2EYVTM3Dg@mail.gmail.com>	<20120822032057.GA30871@google.com>	<50345232.4090002@redhat.com>	<20130603195003.GA31275@evergreen.ssec.wisc.edu>	<20141114163053.GA6547@cosmos.ssec.wisc.edu>	<20141117160212.b86d031e1870601240b0131d@linux-foundation.org>	<20141118014135.GA17252@cosmos.ssec.wisc.edu>	<546AB1F5.6030306@redhat.com>	<20141118121936.07b02545a0684b2cc839a10c@linux-foundation.org>	<CALYGNiMxnxmy-LyJ4OT9OoFeKwTPPkZMF-bJ-eJDBFXgZQ6AEA@mail.gmail.com>	<CALYGNiM_CsjjiK_36JGirZT8rTP+ROYcH0CSyZjghtSNDU8ptw@mail.gmail.com>	<546BDB29.9050403@suse.cz>	<CALYGNiOHXvyqr3+Jq5FsZ_xscsXwrQ_9YCtL2819i6iRkgms2w@mail.gmail.com>	<546CC0CD.40906@suse.cz>	<CALYGNiO9_bAVVZ2GdFq=PO2yV3LPs2utsbcb2pFby7MypptLCw@mail.gmail.com>	<CANN689G+y77m2_paF0vBpHG8EsJ2-pEnJvLJSGs-zHf+SqTEjQ@mail.gmail.com> <CALYGNiOC4dEzzVzSQXGC4oxLbgp=8TC=A+duJs67jT97TWQ++g@mail.gmail.com>
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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.

It may even be possible to not create a child anon_vma for the
first child a parent forks, but only create a new anon_vma once
the parent clones a second child (alive at the same time as the
first child).

That still takes care of things like apache or sendmail, but
would not create infinite anon_vmas for a task that keeps forking
itself to infinite depth without calling exec...

- -- 
All rights reversed
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