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Date: Tue, 31 Jan 2006 12:47:51 -0600
From: Brian Twichell <tbrian@us.ibm.com>
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To: Ray Bryant <raybry@mpdtxmail.amd.com>
CC: Hugh Dickins <hugh@veritas.com>, Dave McCracken <dmccr@us.ibm.com>,
       Andrew Morton <akpm@osdl.org>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Linux Memory Management <linux-mm@kvack.org>
Subject: Re: [PATCH/RFC] Shared page tables
References: <A6D73CCDC544257F3D97F143@[10.1.1.4]> <Pine.LNX.4.61.0601202020001.8821@goblin.wat.veritas.com> <43DAA3C9.9070105@us.ibm.com> <200601301246.27455.raybry@mpdtxmail.amd.com>
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Ray Bryant wrote:

>On Friday 27 January 2006 16:50, Brian Twichell wrote:
><snip>
>
>  
>
>>Hi,
>>
>>We collected more granular performance data for the ppc64/hugepage case.
>>
>>CPI decreased by 3% when shared pagetables were used.  Underlying this was
>>a 7% decrease in the overall TLB miss rate.  The TLB miss rate for
>>hugepages decreased 39%.  TLB miss rates are calculated per instruction
>>executed.
>>
>>    
>>
>
>Interesting.
>
>Do you know if Dave's patch supports sharing of pte's for 2 MB pages on 
>X86_64?
>  
>
I believe it does.  Dave, can you confirm ?

>Was there a corresponding improvement in overall transaction throughput for 
>the hugetlb, shared pte case?    That is, did the 3% improvement in CPI 
>translate to a measurable improvement in the overall OLTP benchmark score?
>  
>
Yes.  My original post with performance data described a 3% improvement
in the ppc64/hugepage case.  This is a transaction throughput statement.

>(I'm assuming your 25-50% improvement measurements, as mentioned in a previous 
>note, was for small pages.)
>
>  
>
That's correct.


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