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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 11:01:05
Message-ID: 1271588465.8305.13998.camel@ebony (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sun, 2010-04-18 at 08:24 +0100, Simon Riggs wrote:
> 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.

v2 patch attached

-- 
 Simon Riggs           www.2ndQuadrant.com

Attachment: knownassigned_sortedarray.v2.diff
Description: text/x-patch (35.0 KB)

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