linux-kernel - Re: [PATCH] mremap: enforce rmap src/dst vma ordering in case of vma_merge succeeding in copy

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Date:	Fri, 04 Nov 2011 16:59:26 +0100
From:	Pawel Sikora <pluto@...k.net>
To:	Nai Xia <nai.xia@...il.com>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	jpiszcz@...idpixels.com, arekm@...-linux.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mremap: enforce rmap src/dst vma ordering in case of vma_merge succeeding in copy_vma

On Friday 04 of November 2011 22:34:54 Nai Xia wrote:
> On Fri, Nov 4, 2011 at 3:31 PM, Hugh Dickins <hughd@...gle.com> wrote:
> > On Mon, 31 Oct 2011, Andrea Arcangeli wrote:
> >
> >> migrate was doing a rmap_walk with speculative lock-less access on
> >> pagetables. That could lead it to not serialize properly against
> >> mremap PT locks. But a second problem remains in the order of vmas in
> >> the same_anon_vma list used by the rmap_walk.
> >
> > I do think that Nai Xia deserves special credit for thinking deeper
> > into this than the rest of us (before you came back): something like
> >
> > Issue-conceived-by: Nai Xia <nai.xia@...il.com>
> 
> Thanks! ;-)

hi all,

i'm still testing anon_vma_order_tail() patch. 10 days of heavy processing
and machine is still stable but i've recorded some interesting thing:

$ uname -a
Linux hal 3.0.8-vs2.3.1-dirty #6 SMP Tue Oct 25 10:07:50 CEST 2011 x86_64 AMD_Opteron(tm)_Processor_6128 PLD Linux
$ uptime
 16:47:44 up 10 days,  4:21,  5 users,  load average: 19.55, 19.15, 18.76
$ ps aux|grep migration
root         6  0.0  0.0      0     0 ?        S    Oct25   0:00 [migration/0]
root         8 68.0  0.0      0     0 ?        S    Oct25 9974:01 [migration/1]
root        13 35.4  0.0      0     0 ?        S    Oct25 5202:15 [migration/2]
root        17 71.4  0.0      0     0 ?        S    Oct25 10479:10 [migration/3]
root        21 70.7  0.0      0     0 ?        S    Oct25 10370:14 [migration/4]
root        25 66.1  0.0      0     0 ?        S    Oct25 9698:11 [migration/5]
root        29 70.1  0.0      0     0 ?        S    Oct25 10283:22 [migration/6]
root        33 62.6  0.0      0     0 ?        S    Oct25 9190:28 [migration/7]
root        37  0.0  0.0      0     0 ?        S    Oct25   0:00 [migration/8]
root        41 97.7  0.0      0     0 ?        S    Oct25 14338:30 [migration/9]
root        45 29.2  0.0      0     0 ?        S    Oct25 4290:00 [migration/10]
root        49 68.7  0.0      0     0 ?        S    Oct25 10081:38 [migration/11]
root        53 98.7  0.0      0     0 ?        S    Oct25 14477:25 [migration/12]
root        57 70.0  0.0      0     0 ?        S    Oct25 10272:57 [migration/13]
root        61 69.7  0.0      0     0 ?        S    Oct25 10232:29 [migration/14]
root        65 70.9  0.0      0     0 ?        S    Oct25 10403:09 [migration/15]

wow, 71..241 hours in migration processes after 10 days of uptime?
machine has 2 opteron nodes with 32GB ram paired with each processor.
i suppose that it spends a lot of time on migration (processes + memory pages).

BR,
Paweł.
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