linux-kernel - Re: [regression] commit 6a4f3b52 causes invalid memtype

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Message-ID: <4C329450.2010703@redhat.com>
Date:	Tue, 06 Jul 2010 10:26:24 +0800
From:	Xiaotian Feng <dfeng@...hat.com>
To:	Ali Gholami Rudi <ali@...i.ir>
CC:	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, x86@...nel.org,
	venki@...gle.com, tglx@...utronix.de, suresh.b.siddha@...el.com,
	mingo@...hat.com, linux-kernel@...r.kernel.org, hpa@...or.com
Subject: Re: [regression] commit 6a4f3b52 causes invalid memtype

On 07/05/2010 07:38 PM, Ali Gholami Rudi wrote:
> Ingo Molnar<mingo@...e.hu>  wrote:
>>>>>> commit 2463eb8b3093995e09a0d41b3d78ee0cf5fb4249
>>>>>> Author: Peter Zijlstra<peterz@...radead.org>
>>>>>> Date:   Sat May 29 15:31:43 2010 +0200
>>>>>>
>>>>>>        rbtree: Undo augmented trees performance damage
>>>>>
>>>>> Where can I get it?  I couldn't find it either in
>>>>> Linus' or x86 repo tip.
>>>> http://git.kernel.org/tip/2463eb8b3093995e09a0d41b3d78ee0cf5fb4249
>>>
>>> It does fix it.
>>
>> Hm, interesting. That's a pure performance fix - so why does it fix a
>> regression?
>>
>> Does Peter's augmented rbtrees improvements fix a bug too, as a side-effect?
>> If yes then we need to accelerate that commit - right now it's aimed for
>> v2.6.36.
>
> Since the bug appears after commit 6a4f3b52, it seems to be
> related to the value of memtype->subtree_max_end.  Peter's
> patch seems to change the way memtype->subtree_max_end is
> updated, which seems to fix the problem too.

Actually, this exposed a bug in augmented rbtree 
(http://lkml.org/lkml/2010/6/21/459).
With commit 6a4f3b52, the bug was easier to trigger :-)

>
> Thanks,
> Ali
>
>

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