Re: Queries becoming slow under heavy load

From: Ivan Voras
Subject: Re: Queries becoming slow under heavy load
Date: ,
Msg-id: ihp7bt$quc$1@dough.gmane.org
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In response to: Queries becoming slow under heavy load  ("Anne Rosset")
Responses: Re: Queries becoming slow under heavy load  ("mark")
List: pgsql-performance

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Queries becoming slow under heavy load  ("Anne Rosset", )
 Re: Queries becoming slow under heavy load  (Andy Colson, )
 Re: Queries becoming slow under heavy load  ("Kevin Grittner", )
 Re: Queries becoming slow under heavy load  ("Ing. Marcos Ortiz Valmaseda", )
 Re: Queries becoming slow under heavy load  (Ivan Voras, )
  Re: Queries becoming slow under heavy load  ("mark", )
 FW: Queries becoming slow under heavy load  ("Anne Rosset", )
  Re: FW: Queries becoming slow under heavy load  (Shaun Thomas, )
   Re: FW: Queries becoming slow under heavy load  (Scott Marlowe, )
  Re: FW: Queries becoming slow under heavy load  (Scott Marlowe, )
   Re: FW: Queries becoming slow under heavy load  ("Anne Rosset", )
    Re: FW: Queries becoming slow under heavy load  (Shaun Thomas, )
     Re: FW: Queries becoming slow under heavy load  (Mladen Gogala, )
     Re: FW: Queries becoming slow under heavy load  ("Anne Rosset", )
      Re: FW: Queries becoming slow under heavy load  (Scott Marlowe, )

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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From: Shaun Thomas
Date:
Subject: Re: FW: Queries becoming slow under heavy load
From: David Greco
Date:
Subject: Real vs Int performance