Message-ID: <525C8223.9080900@fuzzy.cz>
Date: Tue, 15 Oct 2013 01:45:39 +0200
From: Tomas Vondra <tv@fuzzy.cz>
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To: pgsql-performance@postgresql.org
Subject: Re: CPU spikes and transactions
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On 15.10.2013 01:26, Tony Kay wrote:
> Hi Calvin,
> 
> Yes, I have sar data on all systems going back for years. 
> 
> Since others are going to probably want to be assured I am really
> "reading the data" right:
> 
> - This is 92% user CPU time, 5% sys, and 1% soft
> - On some of the problems, I _do_ see a short spike of pgswpout's
> (memory pressure), but again, not enough to end up using much system time
> - The database disks are idle (all data being used is in RAM)..and are
> SSDs....average service times are barely measurable in ms.

OK. Can you share the data? Maybe we'll notice something suspicious.

> If I had to guess, I'd say it was spinlock misbehavior....I cannot 
> understand why ekse a transaction blocking other things would drive
> the CPUs so hard into the ground with user time.

Have you tried running perf, to verify the time is actually spent on
spinlocks?

Tomas


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