Re: [PATCH/RFC] Shared page tables

From: Brian Twichell <tbrian@xxxxxxxxxx>
Date: Tue, 31 Jan 2006 12:47:51 -0600

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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Follow-Ups:
- Re: [PATCH/RFC] Shared page tables
  - From: Dave McCracken

References:
- [PATCH/RFC] Shared page tables
  - From: Dave McCracken
- Re: [PATCH/RFC] Shared page tables
  - From: Hugh Dickins
- Re: [PATCH/RFC] Shared page tables
  - From: Brian Twichell
- Re: [PATCH/RFC] Shared page tables
  - From: Ray Bryant

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