Re: [PATCH/RFC] Shared page tables

Ray Bryant
2006-01-30T18:46:24Z

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
>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: email@kvack.org

--
Ray Bryant
AMD Performance Labs Austin, Tx
512-602-0038 (o) 512-507-7807 (c)