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Re: Scalability in postgres

From: Scott Mead <scott(dot)lists(at)enterprisedb(dot)com>
To: Fabrix <fabrixio1(at)gmail(dot)com>
Cc: David Rees <drees76(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Scalability in postgres
Date: 2009-05-28 20:59:05
Message-ID: d3ab2ec80905281359s671dfdeag32555312cc40b982@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Thu, May 28, 2009 at 4:53 PM, Fabrix <fabrixio1(at)gmail(dot)com> wrote:

>
>
>>
>> Wow, that's some serious context-switching right there - 300k context
>> switches a second mean that the processors are spending a lot of their
>> time fighting for CPU time instead of doing any real work.
>
>
  There is a bug in the quad core chips during a massive amount of
connections that will cause all cores to go to 100% utilization and no work
be done.  I'm digging to find links, but if I remember correctly, the only
way to fix it was to disable the 4th core in linux (involved some black
magic in /proc).  You really need to lower the number of processes you're
forcing each processor bus to switch through (or switch to AMD's
hyper-transport bus).


>
>>
>> It appears that you have the server configured with a very high number
>> of connections as well?  My first suggestion would be to look at a way
>> to limit the number of active connections to the server at a time
>> (pgPool or similar).
>
>
> yes, i have max_connections = 5000
> can lower, but at least i need 3500 connections
>

Typically, it's a bad idea to run run with anything over 1000 connections
(many will suggest lower than that).  If you need that many connections,
you'll want to look at a connection pool like pgBouncer or pgPool.

--Scott

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