Negative caching

[Cameron Hutchison]

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.