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From:  Raistlin <>
To:  Peter Zijlstra <>
Subject:  [RFC 0/12][PATCH] SCHED_DEADLINE (new version of SCHED_EDF)
Date:  Fri, 16 Oct 2009 17:35:24 +0200
Message-ID:  <1255707324.6228.448.camel@Palantir>
Cc:, linux-kernel <>, michael trimarchi <>, Fabio Checconi <>, Ingo Molnar <>, Thomas Gleixner <>, Dhaval Giani <>, Johan Eker <>, "p.faure" <>, Chris Friesen <>, Steven Rostedt <>, Henrik Austad <>, Frederic Weisbecker <>, Darren Hart <>, Sven-Thorsten Dietrich <>, Bjoern Brandenburg <>, Tommaso Cucinotta <>, "giuseppe.lipari" <>, Juri Lelli <>
Archive-link:  Article

Hi Peter, Hi all,

Given all the comments and feedback we got, here it is the new version
of our EDF patch, this time in a split series. :-)

Special thanks to all the one that gave us any kind of suggestion,
especially during last RTLWS in Dresden.

The rationale/motivation for the new scheduler is the same of the first
e-mail (, thus I only add some new and
(I think) interesting links:
 - Ericsson posting about SCHED_EDF/DEADLINE

 - The slides we presented at RTLWS in Dresden:

 - Luca Abeni's presentation about using deadline based reservation 
   schedulers for IRQ-Threads:

Moreover, we moved the project on, therefore:

I am also setting up right now the Wiki section, where you can find some
more detailed usage instructions, examples and overhead estimation:

Git repositories are up and running, and ready at:
 git:// sched-deadline 

 git:// sched-devel-deadline

(preempt-rt [*])
 git:// rt-deadline

The new project homepage is

Here the main changes we did, following what many of you --and mainly
Peter-- suggested:
- name changed from SCHED_EDF to SCHED_DEADLINE

- SCHED_DEADLINE has higher priority than SCHED_FIFO/SCHED_RR

- flags added in sched_param_ex to signal deadline misses
  (in case of utilization > 100%) and/or budget overruns

- new sched_*_ex prototypes, with a len field to accomodate the size of
  sched_param_ex, trying to avoid further ABI issues if it changes

- new syscall sched_wait_interval added. It behaves like clock_nanosleep
  but, for a SCHED_DEADLINE task, it also represent the end of the
  current instance (sched_yield no longer needed)

- on fork, child starts but with 0 bandwidth (i.e., it does not start! :-D)

- bug fixing :)

Any feedback and contribution is welcome.

Many thanks,

             Dario Faggioli
             Claudio Scordino
             Michael Trimarchi

[*] porting toward preempt-rt is work in progress. Code is there, but we
are testing and fixing it, with the help of Luca and Nicola from
Trento... So don't consider it as the final version!

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