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Re: Storing hot members of PGPROC out of the band

From: Jim Nasby <jim(at)nasby(dot)net>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Storing hot members of PGPROC out of the band
Date: 2011-12-17 06:00:30
Message-ID: 85C5CFD4-0395-409A-B372-2473BBE5E83C@nasby.net (view raw or flat)
Thread:
Lists: pgsql-hackers
On Dec 16, 2011, at 7:25 PM, Bruce Momjian wrote:
> Robert Haas wrote:
>> On that theory, I'm inclined to think that's not really a problem.
>> We'll go nuts if we refuse to commit anything until it shows a
>> meaningful win on every imaginable workload, and it seems like this
>> can't really be worse than the status quo; any case where it is must
>> be some kind of artifact.  We're better of getting rid of as much
>> ProcArrayLock contention as possible, rather than keeping it around
>> because there are corner cases where it decreases contention on some
>> other lock.
> 
> Interesting conclusion, and it makes sense.  Seems once this is applied
> we will have more places to look for contention improvements.

I also wonder how much this throws some previous performance tests into suspicion. If it's not uncommon for performance improvement attempts to shift a bottleneck to a different part of the system and marginally hurt performance then we might be throwing away good performance improvement ideas before we should...
--
Jim C. Nasby, Database Architect                   jim(at)nasby(dot)net
512.569.9461 (cell)                         http://jim.nasby.net



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