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Re: spinlock contention

From: Florian Pflug <fgp(at)phlo(dot)org>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Merlin Moncure <mmoncure(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: spinlock contention
Date: 2011-06-28 21:55:16
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Lists: pgsql-hackers
On Jun28, 2011, at 23:48 , Robert Haas wrote:
> On Tue, Jun 28, 2011 at 5:33 PM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
>> On Tue, Jun 28, 2011 at 3:18 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>>> user-32: none(1.0),atomicinc(14.4),pg_lwlock_cas(22.1),cmpxchng(41.2),pg_lwlock(588.2),spin(1264.7)
>> I may not be following all this correctly, but doesn't this suggest a
>> huge potential upside for the cas based patch you posted upthread when
>> combined with your earlier patches that were bogging down on spinlock
>> contentionl?
> Well, you'd think so, but in fact that patch makes it slower.  Don't
> ask me why, 'cuz I dunno.  :-(

Huh? Where do you see your CAS patch being slower than unpatched LWLocks
in these results? Or are you referring to pgbench runs you made, not
to these artificial benchmarks?

best regards,
Florian Pflug

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