[TriLUG] Growing OS cache in RAM causing high system CPU usage

[Michael Peters]

On Tue, Jul 8, 2014 at 12:49 PM, Daniel Sterling
<sterling.daniel at gmail.com> wrote:
> do you have a swap partition set up; look like no?

Right, no swap on this machine.

> This behaviour sounds like what happens when a box has used up all its
> RAM and swap.

It's used up all of it's "free" RAM, but ~2/3 of the RAM in use is
actually OS cache which should just
seemlessly transfer over to applications that request it right?
Everything I've experienced and read says it doesn't matter how much
RAM the OS is using for cache because it will just give it to
applications when needed without a problem. But it's definitely a
problem because the system CPU usage goes through the roof (with
minimal IO).

> Try making OOM killer more aggressive

There's nothing to kill. 1/3 of the RAM is being used by the
application and shouldn't be killed. 2/3 is system cache.

> and/or disabling overcommit

I've thought about disabling overcommit, but wanted to hear more
reasons why that would be a good thing before I tried it.

> and/or adding swap

I don't think adding swap would help since it's not actually running
out of memory (at least when you consider OS cache as "free").