lkml.org 
[lkml]   [1998]   [Oct]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: a different approach to scheduling issues

On 02-Oct-98 Rik van Riel wrote:
>> It's quite common for systems to only recalculate priorities every
>> second or so, even if they're switching contexts much more rapidly.
>> This allows you to do more interesting/complex scheduling decisions
>> without everything bogging down. Maybe you could even run the
>> scheduler in user-mode as an RT task...
>
> Hmm. Although it is an interesting idea, it kinda conflicts
> with the next part of your message...

How so?

>> Every now and then (a tunable which depends on how responsive you
>> need your dynamic priorities to be) you go through and recalculate
>> the relative importance of your running processes.
>
> This is in my patch. It recalculates the importance of
> only the running processes as soon as each process on
> the runqueue has used up it's timeslice.

That's a little more often than I'm talking about. You divide your scheduler
into two parts: one which makes sure processes get CPU at a certain rate, and
another which assigns what rate processes should get CPU at. The former is a
pretty simple procedure which can be implemented by controlling the placement
of processes on the run-queue, and has to be performed whenever something gets
put on the run-queue. The latter process can be done less frequently, and
calculated based on the behaviour of the process since the last calculation
(and other factors). By "less frequently", I mean somewhere in the order of
.1-10 seconds, depending on what the nature of the machine's load is.

>> RT processes, of course, never have their priorities changed, so the
>> scheduler is essentially a no-op. Sleeping processes never need
>> their priorities adjusted until they actually become runnable.
>
> Hey, I did that first! :-) This is in my patch
> as well...

Well, yes, it was something that needed doing. I was pleased to see it in your
patch.

J

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:44    [W:1.412 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site