[Linux-ia64] Re: web page on O(1) scheduler

Mike Galbraith
2003-05-21T20:46:15Z

At 10:56 AM 5/21/2003 -0700, David Mosberger wrote:
> >>>>> On Wed, 21 May 2003 11:26:31 +0200, Mike Galbraith <efault@gmx.de>
> said:
>
> Mike> The page mentions persistent starvation. My own explorations
> Mike> of this issue indicate that the primary source is always
> Mike> selecting the highest priority queue.
>
>My working assumption is that the problem is a bug with the dynamic
>prioritization. The task receiving the signals calls sleep() after
>handling a signal and hence it's dynamic priority should end up higher
>than the priority of the task sending signals (since the sender never
>relinquishes the CPU voluntarily).

The only thing that matters is how much you sleep vs run, so yes, it should
have a higher priority unless that handling is heavy on cpu. If it
doesn't, then you have to have a different problem, because the dynamic
priority portion of the scheduler is dead simple. The only way I can
imagine that priority could end up lower than expected is heavyweight
interrupt load, or spinning out of control.

>However, I haven't actually had time to look at the relevant code, so
>I may be missing something. If you understand the issue better,
>please explain to me why this isn't a dynamic priority issue.

I just saw your other post regarding the web page. Now that I know that
there's a detailed description in there somewhere, I'll go read it and see
if any of what I've gleaned from crawling around the scheduler code is
useful. I thought you might be encountering the same kind of generic
starvation I've seen. Ergo, the simple diag patch.

-Mike