> -----Original Message-----
> From: Greg Stark [mailto:gsstark@mit.edu]
> Sent: Monday, March 07, 2005 12:06 PM
> To: John A Meinel
> Cc: Tom Lane; Magnus Hagander; Ken Egervari;
> pgsql-performance@postgresql.org; pgsql-hackers-win32@postgresql.org
> Subject: Re: [pgsql-hackers-win32] [PERFORM] Help with tuning
> this query (with
> [...]
> What would be really neato would be to use the rtdsc (sp?) or
> equivalent assembly instruction where available. Most processors
> provide such a thing and it would give much lower overhead and much
> more accurate answers.
>
> The main problem I see with this would be on multi-processor
> machines. (QueryPerformanceCounter does work properly on
> multi-processor machines, right?)

I believe QueryPerformanceCounter() already does this.

__
David B. Held
Software Engineer/Array Services Group
200 14th Ave. East, Sartell, MN 56377
320.534.3637 320.253.7800 800.752.8129

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"Dave Held" <dave.held@arrayservicesgrp.com> writes:

> > What would be really neato would be to use the rtdsc (sp?) or
> > equivalent assembly instruction where available. Most processors
> > provide such a thing and it would give much lower overhead and much
> > more accurate answers.
> >
> > The main problem I see with this would be on multi-processor
> > machines. (QueryPerformanceCounter does work properly on
> > multi-processor machines, right?)
>
> I believe QueryPerformanceCounter() already does this.

This would be a good example of why selectively quoting the part of the
message to which you're responding to is more useful than just blindly echoing
my message back to me.

Already does what?

Use rtdsc? In which case using it would be a mistake. Since rtdsc doesn't work
across processors. And using it via QueryPerformanceCounter would be a
non-portable approach to using rtdsc. Much better to devise a portable
approach that works on any architecture where something equivalent is
available.

Or already works on multi-processor machines? In which case, uh, ok.


--
greg


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