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Re: Spinlock performance improvement proposal

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Spinlock performance improvement proposal
Date: 2001-09-29 19:32:49
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Lists: pgsql-hackers
OK, testing now with 1000 backends and 2000 buffers.  Will report.

> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > No scale factor, as I illustrated from the initialization command I
> > used.  Standard buffers too.  Let me know what values I should use for
> > testing.
> Scale factor has to be >= max number of clients you use, else you're
> just measuring serialization on the "branch" rows.
> I think the default NBuffers (64) is too low to give meaningful
> performance numbers, too.  I've been thinking that maybe we should
> raise it to 1000 or so by default.  This would trigger startup failures
> on platforms with small SHMMAX, but we could tell people to use -B until
> they get around to fixing their kernel settings.  It's been a long time
> since we fit into a 1-MB shared memory segment at the default settings
> anyway, so maybe it's time to select somewhat-realistic defaults.
> What we have now is neither very useful nor the lowest common
> denominator...
> 			regards, tom lane

  Bruce Momjian                        |
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  +  If your life is a hard drive,     |  830 Blythe Avenue
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