Re: [Q] Lowest scheduling priority
From: Sci-col (grobyn_at_telus.net)
Date: 11/29/03
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- In reply to: Fredderic: "Re: [Q] Lowest scheduling priority"
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Date: Sat, 29 Nov 2003 07:16:13 GMT
Fredderic wrote:
> On Thu, 13 Nov 2003 13:16:33 -0500, Steve Ackman wrote:
>
>
>>>Is there a way to set the priority of a process so low that it only uses
>>>processor cycles that would have gone idle anyway?
>>
>> I don't think your problem is niceness, but RAM
>>shortage. I used to run seti at nice 19, and
>>experienced delays in higher priority processes. It
>>was due to memory management. Once I doubled my RAM,
>>there was enough memory for all the processes to have
>>their own, so there was no need for them to share it.
>>Everything sped up considerably.
>
>
> On my machine, I have more than enough RAM (until I started leaving
> Mozilla running for a week on end, I hadn't realized I'd stuffed up my
> fstab and it wasn't even mounting a swap).
>
> It seems as far as I can tell, that a n-19 task will still steal some
> processor time from other apps. One of my favorite little arcade
> style games consumes every ounce of available CPU power, keeping the frame
> rate as high as possible. With not much else in the way of active
> processes, it seems to run very close to 100%. With seti running, it gets
> a significantly lower amount of CPU time, with seti getting the rest.
>
> This is consistent with the scheduler trying to avoid allowing processes
> to become starved for CPU time (by a method known as aging). Since seti
> is a predominantly maths application, it gets handed control every so
> often by the scheduler (just in case), and runs for its full allowed
> time slice (whereas many nice'd processes will frequently end up doing
> disk I/O or similar that relinquishes the CPU back to the higher priority
> task almost immediately).
>
> What I (and the OP, as best I can tell) want, is a way to stop the
> scheduler from giving seti ANY time slices unless nothing else at all
> wants them. I have considered writing a small daemon to stop seti when
> the processor utilization goes above 30%, and restart it again once it
> drops below 10%, but the current situation isn't really that big of an
> issue anyhow.
>
>
> Fredderic
hint: During the scheduling process (best candidate to be scheduled) is
set to the idle task of this cpu. However, the goodness of this
candidate is set to a very low value (-1000), in hope that there is
someone better than that.
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