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

[Daniel Sterling]

disabling overcommit would cause linux to not allocate more RAM than
it has; I have to assume that's why it's running slowly. and/or you're
hitting a bug. try setting up a small swap file or partition. if linux
can swap just a bit it might be happier. I've nothing technical to
back that up other than knowing there have been previous bugs that
manifest when there is no swap

-- Dan


On Tue, Jul 8, 2014 at 1:07 PM, Michael Peters
<michael00peters at gmail.com> wrote:
> 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").
> --
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