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Re: testing HS/SR - 1 vs 2 performance

Simon Riggs <simon@2ndquadrant.com>

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From: Simon Riggs <simon@2ndQuadrant.com>
To: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
Cc: Erik Rijkers <er@xs4all.nl>, Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, pgsql-hackers@postgresql.org
Date: 2010-05-04T20:48:07Z
Lists: pgsql-hackers

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On Tue, 2010-05-04 at 21:34 +0200, Stefan Kaltenbrunner wrote:

> FWIW - I'm seeing a behaviour here under pgbench -S workloads that looks 
> kinda related.
> 
> using -j 16 -c 16 -T 120 I get either 100000tps and around 660000 
> contextswitches per second or on some runs I end up with 150000tps and 
> around 1M contextswitches/s sustained. I mostly get the 100k result but 
> once in a while I get the 150k one. And one even can anticipate the 
> final transaction rate from watching "vmstat 1"...
> 
> I'm not sure yet on what is causing that behaviour but that is with 
> 9.0B1 on a Dual Quadcore Nehalem box with 16 cpu threads (8+HT) on a 
> pure in-memory workload (scale = 20 with 48GB RAM).

Educated guess at a fix: please test this patch. It's good for
performance testing, but doesn't work correctly at failover, which would
obviously be addressed prior to any commit.

-- 
 Simon Riggs           www.2ndQuadrant.com