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Re: a heavy duty operation on an "unused" table kills my server

From: Greg Smith <greg(at)2ndquadrant(dot)com>
To: Andy Colson <andy(at)squeakycode(dot)net>
Cc: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>, pgsql-performance(at)postgresql(dot)org
Subject: Re: a heavy duty operation on an "unused" table kills my server
Date: 2010-01-14 18:30:46
Message-ID: 4B4F62D6.7020104@2ndquadrant.com (view raw or flat)
Thread:
Lists: pgsql-performance
Andy Colson wrote:
> So if there is very little io, or if there is way way too much, then 
> the scheduler really doesn't matter.  So there is a slim middle ground 
> where the io is within a small percent of the HD capacity where the 
> scheduler might make a difference?

That's basically how I see it.  There seem to be people who run into 
workloads in the middle ground where the scheduler makes a world of 
difference.  I've never seen one myself, and suspect that some of the 
reports of deadline being a big improvement just relate to some buginess 
in the default CFQ implementation that I just haven't encountered.

-- 
Greg Smith    2ndQuadrant   Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com  www.2ndQuadrant.com


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Subject: Re: bad execution plan for subselects containingwindowing-function
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Subject: Re: Slow "Select count(*) ..." query on table with 60 Mio. rows

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