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Re: testing HS/SR - 1 vs 2 performance

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Erik Rijkers <er(at)xs4all(dot)nl>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: testing HS/SR - 1 vs 2 performance
Date: 2010-04-18 07:24:36
Message-ID: 1271575476.8305.13528.camel@ebony (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Sat, 2010-04-17 at 18:52 -0400, Tom Lane wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> > What I'm not clear on is why you've used a spinlock everywhere when only
> > weak-memory thang CPUs are a problem. Why not have a weak-memory-protect
> > macro that does does nada when the hardware already protects us? (i.e. a
> > spinlock only for the hardware that needs it).
> Well, we could certainly consider that, if we had enough places where
> there was a demonstrable benefit from it.  I couldn't measure any real
> slowdown from adding a spinlock in that sinval code, so I didn't propose
> doing so at the time --- and I'm pretty dubious that this code is
> sufficiently performance-critical to justify the work, either.

OK, I'll put a spinlock around access to the head of the array.

Thanks for your input.

 Simon Riggs 

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