Re: [gentoo-user] Strive for zero swap usage?

[Jeremi Piotrowski <jeremi.piotrowski@gmail.com>]

On Thu, Oct 06, 2016 at 03:31:59PM -0700, Grant wrote:
> 
> Does this look OK?  It looks to me like heavy swapping in and out with
> plenty of free memory (minus buffers/cache).
> 

Have you looked at the _units_ displayed by vmstat and munin? You're
looking at **kilobytes** being swapped and calling that _heavy swapping_...

In general your system shows that you have a lot of memory used as cache,
and I would guess that the kernel thinks its better to keep using that
memory for caching and swap out the occasional page of application data.
The alternative would be dropping some cache - might be worse for
performance. Swapping does not seem to be something that could be causing
any issues for you.

Do you even have an issue with response times of your webservers? If so
(which you haven't explicitly stated here) it would be better for you to
look at things from that end - what is taking long in the webserver and
what is causing those things to take that long.

As it stands, you're using anti-methods of performance analysis:

    Streetlight Anti-Method:

        1. Pick observability tools there are familiar
        2. Run tools
        3. Look for obvious issues

and
    
    Traffic Light Anti-Method

        1. Open dashboard (munin)
        2. All green? Assume everything is good
        3. Something red? Assume that's a problem

If you're really interested in this kind of stuff I recommend checking out
the materials that Brendan Gregg has gathered over the years.
http://www.brendangregg.com/methodology.html and other links on his page.