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Subject: Re: 2.6.38 sbrk regression
From: raz ben yehuda <raziebe@gmail.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: lkml <linux-kernel@vger.kernel.org>, riel@redhat.com,
        kosaki.motohiro@jp.fujitsu.com, akpm@linux-foundation.org,
        Mel Gorman <mel@csn.ul.ie>
In-Reply-To: <20110413172127.GB5734@random.random>
References: <1302692638.15225.14.camel@raz.scalemp.com>
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	 <1302703579.17536.1.camel@raz.scalemp.com>
	 <20110413172127.GB5734@random.random>
Content-Type: text/plain; charset="UTF-8"
Date: Thu, 14 Apr 2011 11:13:19 +0300
Message-ID: <1302768799.2706.15.camel@raz.scalemp.com>
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Andrea Hello

I performed the second benchmark on 2.6.39-rc3, not 38. I am sorry for
the typo ( dell keyboard is too small ).

1. First benchmark was performed on 2.6.38, no compaction and with
slab=y. regression of 13% compared to 2.6.27

2. second benchmark was performed on 2.6.39-rc3, with compaction and
slab. resulted like 2.6.38, 13% regression compared to 2.6.27. So the
2.6.39-rc1 fix is probably related to something else.

3. It does not matter if i disable thp or not.  regression still exits.

I will update you more in following few days. 

thank you for your help.


On Wed, 2011-04-13 at 19:21 +0200, Andrea Arcangeli wrote:
> On Wed, Apr 13, 2011 at 05:06:19PM +0300, raz ben yehuda wrote:
> > ok, managed to build 38-rc3 ( keep forgetting make mrproper ).
> > problem is still there:
> 
> Oops I thought it was typo on your prev email so I didn't answer
> assuming you would test 39-rc like I suggested in my prev email, I
> really meant 2.6.39-rc3.
> 
> The fix I refer to is d527caf22e48480b102c7c6ee5b9ba12170148f7 and
> it's included in >= 2.6.39-rc1. 38-rc3 has THP but not this
> changeset. We tried to push it for 38 final but it was a bit late so
> it got merged immediately in 39-rc1 to stay on the safe side (it's
> only a performance issue and the other longstanding irq/sched latency
> issues in compaction that got fixed in 39-rc1 where actually more
> relevant than the compaction-kswapd removal).


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