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Re: sudden spurt in swap utilization (was:cpu bound postgresql setup.)

From: Yeb Havinga <yebhavinga(at)gmail(dot)com>
To: Rajesh Kumar Mallah <mallah(dot)rajesh(at)gmail(dot)com>
Cc: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-performance(at)postgresql(dot)org
Subject: Re: sudden spurt in swap utilization (was:cpu bound postgresql setup.)
Date: 2010-06-25 11:28:57
Message-ID: 4C2492F9.2020706@gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
Rajesh Kumar Mallah wrote:
> A scary phenomenon is being exhibited by the server , which is the server
> is slurping all the swap suddenly
>   
>  8  1 4192912 906164   6100 27873640    0    0  2277   858 13440 16235
> 63  8 19 10  0
>
> I reduced work_mem from 4GB to 2GB to 512MB (now). I clearly remember that this
> abnormal consumption of swap was NOT there even when work_mem was 4GB.
> eg during happier times swap utilisation was: http://pastebin.com/bnE1pFZ9
>   
> the question is whats making postgres slurp the swap? i am posting my
> current postgresql.conf
> once again.
>
> # cat postgresql.conf  | grep -v "^\s*#" | grep -v "^\s*$"
> listen_addresses = '*'          # what IP address(es) to listen on;
> port = 5432                             # (change requires restart)
> max_connections = 300                   # (change requires restart)
>   
Hello Rajesh,

In constrast with e.g. shared_buffers and effective_cache_size, work_mem 
is amount of memory per 'thing' (e.g. order/group by) that wants some 
working memory, so even a single backend can use several pieces of 
work_mem memory.

Looking at your postgresql.conf, other memory values seem a bit too high 
as well for a 32GB ram server. It is probably a good idea to use pgtune 
(on pgfoundry) to get some reasonable ball park settings for your hardware.

regards,
Yeb Havinga


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