linux-kernel - Re: regression - slow git rebase performance with 2.6.39-rcX kernel

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Message-ID: <4DA45B12.2090506@fusionio.com>
Date:	Tue, 12 Apr 2011 16:00:50 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Zdenek Kabelac <zdenek.kabelac@...il.com>
CC:	Pekka Enberg <penberg@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>
Subject: Re: regression - slow git rebase performance with 2.6.39-rcX kernel

On 2011-04-12 15:59, Zdenek Kabelac wrote:
> 2011/4/12 Jens Axboe <jaxboe@...ionio.com>:
>> On 2011-04-12 14:51, Pekka Enberg wrote:
>>> Hi,
>>>
>>> [ Fixed your empty CC list. ]
>>>
>>> On Tue, Apr 12, 2011 at 3:45 PM, Zdenek Kabelac
>>> <zdenek.kabelac@...il.com> wrote:
>>>> I'm noticing quite slower speed of my git rebase commands on my git
>>>> tree compared with 2.6.38 kernel.
>>>> I've  T61 with SSD disc drive, ext4 fs, and by default deadline disk
>>>> io scheduler
>>>> The counter showing the number of 'rebased' patches on top of master
>>>> is going much slower.
>>>> When I boot 2.6.38 kernel it's much faster.
>>>>
>>>> Is it a known problem - or do I need to make a bisect ?
>>>
>>> No, I don't think it's a known problem. Git bisect would be helpful,
>>> obviously.
>>
>> Definitely, interesting. Bisect would help. I'll try a similar workload
>> here and see if I see any differences. How big is your rebase, and what
>> are the runtimes (approximately) on .38 vs .39-rc?
>>
> 
> I've made just quick build with the small kernel without debug options
> enable - and the time is then equal with 2.6.38. So the difference is
> probably somewhere in debug build  -  I assume some debug option
> slowed down between 2.6.38 - 2.6.39 significantly.

Good, so it's down to debug. Thanks for testing.

-- 
Jens Axboe

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