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Re: First set of OSDL Shared Mem scalability results, some

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Curt Sampson <cjs(at)cynic(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: First set of OSDL Shared Mem scalability results, some
Date: 2004-10-25 01:49:03
Message-ID: 6097.1098668943@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
Curt Sampson <cjs(at)cynic(dot)net> writes:
> On Sun, 24 Oct 2004, Tom Lane wrote:
>> Considering that the available numbers suggest we could win just a few
>> percent...

> I must confess that I was completely unaware of these "numbers." Where
> do I find them?

The only numbers I've seen that directly bear on the question is
the oprofile results that Josh recently put up for the DBT-3 benchmark,
which showed the kernel copy-to-userspace and copy-from-userspace
subroutines eating a percent or two apiece of the total runtime.
I don't have the URL at hand but it was posted just a few days ago.
(Now that covers all such copies and not only our datafile reads/writes,
but it's probably fair to assume that the datafile I/O is the bulk of it.)

This is, of course, only one benchmark ... but lacking any measurements
in opposition, I'm inclined to believe it.

			regards, tom lane

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