CPU Competition Issue

[steven_nikkel at ertyu.org]

> On 30/10/2012 19:27, Andriy Gapon wrote:
>> on 30/10/2012 03:33 Steven Nikkel said the following:
>>> I'm running a long duration CPU-centric process that will gobble up all
>>> available CPU time. I have it set to run at nice +20. While it's
>>> running I've
>>> noticed other processes have a hard time getting CPU time and run their
>>> activites very slowly. The processes I've noticed issues with are IO
>>> involved,
>>> but they don't appear to be IO blocked as they run dramatically faster
>>> and use
>>> much more CPU time when the CPU intensive process is not running. I
>>> haven't
>>> noticed issues with other processes, but I haven't been looking. If I
>>> push my
>>> CPU intensive process into idle priority 1, all the other processes
>>> return to
>>> their normal behaviour as if it's not running.
>>>
>>> This seems to be a specific behaviour on this one machine running
>>> 9.0-RELEASE-p4
>>> on an Atom 330 dual core. I've tried with and without hyperthreading
>>> enabled
>>> with no noticeable change in behaviour.
>>
>> Can you try with lower nice value, like +10?
>> You want a fix from r228718.  AFAIR, it is not in 9.0.
>>
>
> Could it be cache based? The atom's smaller cache causing more cache
> misses.
>
> Would you be running zfs?

I am running ZFS. I've tried with doing the I/O on a UFS volume instead of
ZFS and the behaviour is the same.