Re: [PATCH/RFC] Shared page tables

["Ray Bryant" <raybry@mpdtxmail.amd.com>]

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?

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?

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

> We didn't collect a profile per se, as we would expect a CPI improvement
> of this nature to be spread over a significant number of functions,
> mostly in user-space.
>
> Cheers,
> Brian
>
>
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-- 
Ray Bryant
AMD Performance Labs                   Austin, Tx
512-602-0038 (o)                 512-507-7807 (c)

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