>>>>> "AS" == Andrew Sullivan <[EMAIL PROTECTED]> writes:

AS> On Fri, Aug 29, 2003 at 12:05:03AM -0700, William Yu wrote:
>> We should see a boost when we move to 64-bit Linux and hopefully another 
>> one when NUMA for Linux is production-stable.

AS> According to the people who've worked with SGIs, NUMA actually seems
AS> to make things worse.  It has something to do with how the shared
AS> memory is handled.  You'll want to dig through the -general or
AS> -hackers archives from somewhere between 9 and 14 months ago, IIRC.

I knew my PhD research would one day be good for *something* ...

The basic premise of NUMA is that you can isolate which data belongs
to which processor and put that on memory pages that are local/closer
to it.  In practice, this is harder than it sounds as it requires very
detailed knowledge of the application's data access patterns, and how
memory is allocated by the OS and standard libraries.  Often you end
up with pages that have data that should be local to two different
processors, and that data keeps being migrated (if your NUMA OS
supports page migration) between the two processors or one of them
just gets slow access.

I can't imagine it benefiting postgres given its globally shared
buffers.


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Vivek Khera, Ph.D.                Khera Communications, Inc.
Internet: [EMAIL PROTECTED]       Rockville, MD       +1-240-453-8497
AIM: vivekkhera Y!: vivek_khera   http://www.khera.org/~vivek/

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