Re: PostgreSQL on multi-CPU systems

Thus spake Tom Lane
> Tatsuo Ishii <t-ishii@sra.co.jp> writes:
> > I have tested PostgreSQL with 2-4 CPU linux boxes. In summary, 2 CPU
> > was a big win, but 4 was not. I'm not sure where the bottle neck is
> > though.
> 
> Our not-very-good implementation of spin locking (using select() to
> wait) might have something to do with this.  Sometime soon I'd like to
> look at using POSIX semaphores where available, instead of spinlocks.

One thing I notice is that a single query can seem to block other queries,
at least to some extent.  It makes me wonder if we effectively have a
single threaded system.  In fact, I have some simple queries that if
I send a bunch at once, the first one can take 15 seconds while the
others zip through.  Is this related to what you are talking about?

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