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SubjectRe: Priority Inversion in Scheduling
At 07:35 AM 9/10/2003, Mike Fedyk wrote:
>On Wed, Sep 10, 2003 at 06:42:10AM +0200, Mike Galbraith wrote:
> > At 02:23 AM 9/10/2003, Nick Piggin wrote:
> > >Hi John,
> > >Your mechanism is basically "backboost". Its how you get X to keep a
> > >high piroirity, but quite unpredictable. Giving a boost to a process
> > >holding a semaphore is an interesting idea, but it doesn't address the
> > >X problem.
> >
> > FWIW, I tried the hardware usage bonus thing, and it does cure the X
> > inversion problem (yeah, it's a pretty cheezy way to do it). It also
> > cures xmms skips if you can't get to the top without hw usage. I also
> > tried a cpu limited backboost from/to tasks associated with hardware, and
> > it hasn't run amok... yet ;-)
>
>Against which scheduler, and when are you going to post the patch?

Against stock test-4, but I'm not going to post it. It's just an
experiment to verify that there is another simple way to defeat the X
inversion problem (while retaining active list requeue). Also, backboost
is a tricky little bugger, and I thought I'd let Nick know that I had some
success with this heavily restricted form. (global backboost can be down
right evil)

If anyone having inversion or concurrency troubles wants to give it a try
for grins, they can drop me a line. My tree tends to morph a lot though,
depending on what aspect of scheduling I'm tinkering with at the time. It
currently does well at defeating known starvation issues, but I don't like
it's priority distribution much (and it's not destined for inclusion, and
it's pretty darn ugly, and I'll likely break it all to pieces again soon,
and...;).

-Mike

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