Re: Some interesting results from tweaking spinlocks

Thanks.  Looks good to me.

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Rod Taylor wrote:
> The number of CPUs on a system should be fairly straight forward to
> find out.  Distributed.net source code has some good examples.
> 
> What I'm not sure of is how well this stuff reacts to CPUs being
> software disabled (Solaris has such a feature).
> 
> ftp://ftp.distributed.net/pub/dcti/source/pub-20010416.tgz
> 
> first function of client/common/cpucheck.cpp
> 
> Each OS gets its own implementation, but they've got all the ones
> Postgresql uses covered off.
> --
> Rod Taylor
> 
> This message represents the official view of the voices in my head
> 
> ----- Original Message -----
> From: "Tom Lane" <tgl@sss.pgh.pa.us>
> To: "Bruce Momjian" <pgman@candle.pha.pa.us>
> Cc: <pgsql-hackers@postgresql.org>
> Sent: Friday, January 04, 2002 11:49 PM
> Subject: Re: [HACKERS] Some interesting results from tweaking
> spinlocks
> 
> 
> > Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > > The difference is small, perhaps 15%.
> >
> > The thing that gets my attention is not that it's so small, it's
> that
> > it is so large.  My expectation was that that code would hardly ever
> > be executed at all, and even less seldom (on a multiprocessor) need
> to
> > block via select().  How is it that *increasing* the delay interval
> > (which one might reasonably expect to simply waste cycles) can
> achieve
> > a 15% improvement in total throughput?  That shouldn't be happening.
> >
> > > My feeling is that we may want to start configuring whether we are
> on
> > > a multi-cpu machine and handle thing differently.
> >
> > That would be more palatable if there were some portable way of
> > detecting it.  But maybe we'll be forced into an "is_smp" GUC
> switch.
> >
> > regards, tom lane
> >
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> 
> 

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