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Re: testing HS/SR - 1 vs 2 performance

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: David Fetter <david(at)fetter(dot)org>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, 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 20:22:21
Message-ID: 1271622141.8305.15238.camel@ebony (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sun, 2010-04-18 at 13:16 -0700, David Fetter wrote:
> On Sun, Apr 18, 2010 at 12:01:05PM +0100, Simon Riggs wrote:
> > 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
> 
> If you've committed this, or any other patch you've sent here,
> *please* mention so on the same thread.

I haven't yet. I've written two patches - this is a major module rewrite
and is still under discussion. The other patch has nothing to do with
this (though I did accidentally include a couple of changes from this
patch and immediately revoked them).

I will wait awhile to see if anybody has some independent test results.

-- 
 Simon Riggs           www.2ndQuadrant.com


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Subject: Re: testing HS/SR - 1 vs 2 performance
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