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Re: Queries becoming slow under heavy load

From: Ivan Voras <ivoras(at)freebsd(dot)org>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Queries becoming slow under heavy load
Date: 2011-01-26 13:25:17
Message-ID: ihp7bt$quc$1@dough.gmane.org (view raw or flat)
Thread:
Lists: pgsql-performance
On 25/01/2011 22:37, Anne Rosset wrote:
> Hi,
>
> We are running some performances tests.  With a lot of concurrent
> access,  queries get very slow. When there is no load, those queries run
> fast.

As others said, you need to stat how many concurrent clients are working 
on the database and also the number of logical CPUs (CPU cores, 
hyperthreading) are present in the machine. So far, as a rule of thumb, 
if you have more concurrent active connections (i.e. doing queries, not 
idling), you will experience a sharp decline in performance if this 
number exceeds the number of logical CPUs in the machine.


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Subject: FW: Queries becoming slow under heavy load
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