Re: RFC for a new Scheduling policy/class in the Linux-kernel

Bjoern B. Brandenburg
2009-07-15T05:46:55Z

Quoting "James H. Anderson" <anderson@cs.unc.edu>:
> Ted Baker did some work on an algorithm called EDZL
> (EDF until zero laxity) that is essentially a hybrid of these two
> algorithms. In simulations we've done (not based on real implementations),
> EDZL exhibits really low tardiness (almost non-existent). EDZL may
> give you the benefits of using laxities where useful and be easier
> to implement (but that's just my guess)

EDZL has nice properties but may be hard to implement efficiently
because it requires (a lot of) fine-grained timers. However, Shinpei
Kato and Nobuyuki Yamasaki (CC'ed) presented an EDZL-derived scheduler
called EDCL at RTCSA'08 that has similar performance guarantees but
only does priority promotions at the release and completion times of
jobs (hence, no additional timers are required).

Global EDF-based Scheduling with Efficient Priority Promotion
Shinpei Kato and Nobuyuki Yamasaki
Proceedings of the 14th International Conference on Embedded and
Real-Time Computing Systems and Applications, pages 197-206. IEEE, 2008.
http://www.ny.ics.keio.ac.jp/members/shinpei/papers/rtcsa08.pdf

I know that Shinpei and friends implemented EDCL on top of LITMUS^RT,
but I never got around to incorporating the patches into the "official"
LITMUS^RT patch. (Sorry, Shinpei!)

Regarding the comments about the availability of academic papers (which
were also voiced repeatedly at OSPERT'09), I'd like to point out that
you can find almost any recent paper by searching for the title with
scholar.google.com and clicking on the "All XYZ versions" link... most
researches make PDFs available on their homepages.

- Björn

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