Re: Linux TOP

On Wed, 21 Oct 2009, Waldomiro wrote:

> top - 16:16:30 up 42 days, 13:23,  4 users,  load average: 3.13, 3.52, 3.36
> Cpu(s):  1.4%us,  1.1%sy,  0.0%ni, 84.4%id, 12.9%wa,  0.0%hi,  0.2%si,  0.0%st
> Mem:  16432240k total, 16344596k used,    87644k free,    27548k buffers
> Swap: 10241428k total,  3680860k used,  6560568k free,  6230376k cached
>
> I'm afraid of two things, one is the "load average", I think 3 is too much

You're at 12.9% waiting for I/O and 84.4% idle.  That means your average
load consists of three processes who are stuck waiting for I/O at any
given time.  The I/O is what you should be worried about, not the load
average.

> another is the "swap", almost 4GB of swap, I think that is too much
> swap.

It does look like your server is using much more RAM than it actually has,
which is the likely reason for all the disk I/O.  If you sort the top
output by memory, you might see why that is.

The information provided by top on Linux isn't very good though; take a
look at /proc/meminfo for more details.  Rather than rely on top's math,
instead I usually capture the output from:

ps -e -o pid,rss,vsz,size,user,cmd

And add things up myself instead, taking into account the shared bits each
of the PostgreSQL processes includes.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD