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Re: [COMMITTERS] pgsql: Optimize commit_siblings in two ways to improve group commit.

From: Greg Smith <greg(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [COMMITTERS] pgsql: Optimize commit_siblings in two ways to improve group commit.
Date: 2010-12-08 20:58:25
Message-ID: 4CFFF171.8030800@2ndquadrant.com (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackers
Tom Lane wrote:
> http://archives.postgresql.org/pgsql-performance/2010-12/msg00073.php
>
> Possibly it should have been posted to -hackers instead, but surely you
> read -performance?
>   

Trying to figure out what exactly commit_delay and commit_siblings did 
under the hood was actually the motivation behind my first foray into 
reading the PostgreSQL source code.  Ever since, I've been annoyed that 
the behavior didn't really help the way it's intended, but was not sure 
what would be better.  The additional input from Jignesh this week on 
the performance list suddenly made it crystal clear what would preserve 
the good behavior he had seen, even improving things for his case, while 
also helping the majority who won't benefit from the commit_delay 
behavior at all a little.  I immediately wrote the patch and breathed a 
sign of relief that it was finally going to get better.

I then posted the patch and added it to the January CF.  Unbeknownst to 
me until today, Simon had the same multi-year "this itches and I can't 
make it stop" feel toward these parameters, and that's how it jumped the 
standard process.

-- 
Greg Smith   2ndQuadrant US    greg(at)2ndQuadrant(dot)com   Baltimore, MD
PostgreSQL Training, Services and Support        www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books


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