Message-ID: <CAPQyPG5c1ADteP_rA2JRqLz88s7ZP_vWAKV-dp2hCSM9bRCpmg@mail.gmail.com>
Date:	Fri, 21 Oct 2011 14:54:29 +0800
From:	Nai Xia <nai.xia@...il.com>
To:	Paweł Sikora <pluto@...k.net>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	jpiszcz@...idpixels.com, arekm@...-linux.org,
	linux-kernel@...r.kernel.org
Subject: Re: kernel 3.0: BUG: soft lockup: find_get_pages+0x51/0x110

2011/10/20 Paweł Sikora <pluto@...k.net>:
> On Wednesday 19 of October 2011 21:42:15 Hugh Dickins wrote:
>> On Wed, 19 Oct 2011, Linus Torvalds wrote:
>> > On Wed, Oct 19, 2011 at 12:43 AM, Mel Gorman <mgorman@...e.de> wrote:
>> > >
>> > > My vote is with the migration change. While there are occasionally
>> > > patches to make migration go faster, I don't consider it a hot path.
>> > > mremap may be used intensively by JVMs so I'd loathe to hurt it.
>> >
>> > Ok, everybody seems to like that more, and it removes code rather than
>> > adds it, so I certainly prefer it too. Pawel, can you test that other
>> > patch (to mm/migrate.c) that Hugh posted? Instead of the mremap vma
>> > locking patch that you already verified for your setup?
>> >
>> > Hugh - that one didn't have a changelog/sign-off, so if you could
>> > write that up, and Pawel's testing is successful, I can apply it...
>> > Looks like we have acks from both Andrea and Mel.
>>
>> Yes, I'm glad to have that input from Andrea and Mel, thank you.
>>
>> Here we go.  I can't add a Tested-by since Pawel was reporting on the
>> alternative patch, but perhaps you'll be able to add that in later.
>>
>> I may have read too much into Pawel's mail, but it sounded like he
>> would have expected an eponymous find_get_pages() lockup by now,
>> and was pleased that this patch appeared to have cured that.
>>
>> I've spent quite a while trying to explain find_get_pages() lockup by
>> a missed migration entry, but I just don't see it: I don't expect this
>> (or the alternative) patch to do anything to fix that problem.  I won't
>> mind if it magically goes away, but I expect we'll need more info from
>> the debug patch I sent Justin a couple of days ago.
>
> the latest patch (mm/migrate.c) applied on 3.0.4 also survives points
> 1) and 2) described previously (https://lkml.org/lkml/2011/10/18/427),
> so please apply it to the upstream/stable git tree.
>
> from the other side, both patches don't help for 3.0.4+vserver host soft-lock

Hi Paweł,

Did your "both" mean that you applied each patch and run the tests separately,
or you applied the both patches and run them together?

Maybe there were more than one bugs dancing but having a same effect,
not fixing all of them wouldn't help at all.

Thanks,

Nai Xia


> which dies in few hours of stressing. iirc this lock has started with 2.6.38.
> is there any major change in memory managment area in 2.6.38 that i can bisect
> and test with vserver?
>
> BR,
> Paweł.
>
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