linux-kernel - Re: 2.6.22 -mm merge plans -- vm bugfixes

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Date:	Fri, 04 May 2007 19:43:41 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	unlisted-recipients:; (no To-header on input)
CC:	Christoph Hellwig <hch@...radead.org>,
	Hugh Dickins <hugh@...itas.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrea Arcangeli <andrea@...e.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: 2.6.22 -mm merge plans -- vm bugfixes

Nick Piggin wrote:
> Nick Piggin wrote:
> 
>> Christoph Hellwig wrote:
> 
> 
>>> Is that every fork/exec or just under certain cicumstances?
>>> A 5% regression on every fork/exec is not acceptable.
>>
>>
>>
>> Well after patch2, G5 fork is 3% and exec is 1%, I'd say the P4
>> numbers will be improved as well with that patch. Then if we have
>> specific lock/unlock bitops, I hope it should reduce that further.
> 
> 
> OK, with the races and missing barriers fixed from the previous patch,
> plus the attached one added (+patch3), numbers are better again (I'm not
> sure if I have the ppc barriers correct though).
> 
> These ops could also be put to use in bit spinlocks, buffer lock, and
> probably a few other places too.
> 
> 2.6.21   1.49-1.51   164.6-170.8   741.8-760.3
> +patch   1.71-1.73   175.2-180.8   780.5-794.2
> +patch2  1.61-1.63   169.8-175.0   748.6-757.0
> +patch3  1.54-1.57   165.6-170.9   748.5-757.5
> 
> So fault performance goes to under 5%, fork is in the noise, exec is
> still up 1%, but maybe that's noise or cache effects again.

OK, with my new lock/unlock_page, dd if=large (bigger than RAM) sparse
file of=/dev/null with an experimentally optimal block size (32K) goes
from 626MB/s to 683MB/s on 2 CPU G5 booted with maxcpus=1.

-- 
SUSE Labs, Novell Inc.
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