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Date: Wed, 12 Jan 2005 10:43:26 -0800
From: Andrew Morton <akpm@osdl.org>
To: Christoph Lameter <clameter@sgi.com>
Cc: nickpiggin@yahoo.com.au, torvalds@osdl.org, ak@muc.de, hugh@veritas.com,
       linux-mm@kvack.org, linux-ia64@vger.kernel.org,
       linux-kernel@vger.kernel.org, benh@kernel.crashing.org
Subject: Re: page table lock patch V15 [0/7]: overview
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Christoph Lameter <clameter@sgi.com> wrote:
>
> > Do we have measurements of the negative and/or positive impact on smaller
>  > machines?
> 
>  Here is a measurement of 256M allocation on a 2 way SMP machine 2x
>  PIII-500Mhz:
> 
>   Gb Rep Threads   User      System     Wall flt/cpu/s fault/wsec
>    0  10    1    0.005s      0.016s   0.002s 54357.280  52261.895
>    0  10    2    0.008s      0.019s   0.002s 43112.368  42463.566
> 
>  With patch:
> 
>   Gb Rep Threads   User      System     Wall flt/cpu/s fault/wsec
>    0  10    1    0.005s      0.016s   0.002s 54357.280  53439.357
>    0  10    2    0.008s      0.018s   0.002s 44650.831  44202.412
> 
>  So only a very minor improvements for old machines (this one from ~ 98).

OK.  But have you written a test to demonstrate any performance
regressions?  From, say, the use of atomic ops on ptes?