User space scheduling, 2nd try

Kevin Elphinstone kevine at
Fri Jan 24 00:52:08 CET 2003

rkaiser at wrote:

Hi Robert,

> . or am I really on uncharted ground here?

No not completely, if you can live with hierarchical proportional share
scheduling, see

Checkout Ford et al. "CPU inheritance scheduling", OSDI 96

and for a look at L4 in particular

Simon Winwood
Flexible scheduling mechanisms in L4, BE Thesis, SCS&E, UNSW, November 2000.

Have a look at Dresden as well for a more real-time slant on scheduling in L4.
I believe they use multi-level round robin and a variation on priority
inheritance (helping). I can't convey the exact details of priority assignment
etc, so your better off having a look yourself.

I believe Jochen envisaged something "better" than proportional share, but
still keeping the flexibility, decomposability, and preserving performance.
However, this never got beyond being a vision except for the existence of
preempters (time slice + total quanta ideas) in V4, which is unfinished work.

	- Kevin

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