Re: Adding more memory = hugh cpu load

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "alexandre - aldeia digital" <adaldeia(at)gmail(dot)com>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Adding more memory = hugh cpu load
Date: 2011-10-10 13:51:08
Message-ID: 4E92B1FC0200002500041C95@gw.wicourts.gov
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alexandre - aldeia digital <adaldeia(at)gmail(dot)com> wrote:

> Yesterday, a customer increased the server memory from 16GB to
> 48GB.

That's usually for the better, but be aware that on some hardware
adding RAM beyond a certain point causes slower RAM access. Without
knowing more details, it's impossible to say whether that's the case
here.

> Today, the load of the server hit 40 ~ 50 points.
> With 16 GB, the load not surpasses 5 ~ 8 points.

Are you talking about "load average", CPU usage, or something else?

> The only parameter that I changed is effective_cache_size (from 14
> GB to 40GB) and shared_buffers (from 1 GB to 5 GB). Setting the
> values back does not take any effect.

What version of PostgreSQL is this? What settings are in effect?
How many user connections are active at one time? How many cores
are there, of what type? What's the storage system? What kind of
load is this?

http://wiki.postgresql.org/wiki/Guide_to_reporting_problems
http://wiki.postgresql.org/wiki/Server_Configuration

-Kevin

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