Negative caching

[Hal Burgiss]

On Wed, Jun 17, 2009 at 11:41:48PM -0000, Cameron Hutchison wrote:
> Hal Burgiss <hal at burgiss.net> writes:
> 
> >I think I've figured out why recent Ubuntu has such abysmal performance. Very
> >cleverly over a period of time, it takes all the free memory and uses it to
> >store useless junk that you will never ever use. [...]
> 
> >MEM | tot  992.4M | free   91.3M | cache 316.9M | buff    3.2M | slab   44.1M
> >SWP | tot    2.9G | free    1.4G |              | vmcom   3.2G | vmlim   3.3G
> 
> It looks like (at least) one of the apps you're running has a memory
> leak. It's not caching that is your issue - you've got about 1/3rd of
> your memory given over to cache. But you have 1.5G of swap used. Caching
> could not have pushed this amount out to swap.
> 
> When it happens again, see if atop can sort by memory usage and see what
> processes are using the most memory. You want the VSZ component,
> although it is likely that the RSS of the culprit will also be quite
> large.

I've looked and looked. Consistently Firefox is the biggest memory hog, but it
rarely gets over 40%. Out of necessity it is restarted frequently. There is
not anything else anywhere close to firefox's usage.

Can there be memory leaks that are not reported anywhere? 

Whatever this is, really kicks in while the system is idle for a long time,
like overnight. When I get up, get my coffee, etc, the system is *very* slow
to respond to anything for a while. With enough usage, my regular programs
work their back into non-swap memory and things are responsive (relatively
speaking, but not like the good old 8.04 days), as long as they are being
used. Now go to work, come back 8 hours later to an extremely sluggish system.
And again with enough usage, the responsiveness slowly comes back. Today it
got unbearable and reboot city.

I don't use a screensaver, so that's not it. 

-- 
Hal