Commit bb4e30a4 authored by Claudio Scordino's avatar Claudio Scordino Committed by Ingo Molnar
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sched/deadline/Documentation: Add overrun signal and GRUB-PA documentation 



Signed-off-by: default avatarClaudio Scordino <claudio@evidence.eu.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1522741362-4542-1-git-send-email-claudio@evidence.eu.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 943d355d

Documentation/scheduler/sched-deadline.txt

+24 −1
Original line number Original line Diff line number Diff line
@@ -49,7 +49,7 @@ CONTENTS 
2.1 Main algorithm

2.1 Main algorithm

------------------

------------------





 SCHED_DEADLINE uses three parameters, named "runtime", "period", and

 SCHED_DEADLINE [18] uses three parameters, named "runtime", "period", and

 "deadline", to schedule tasks. A SCHED_DEADLINE task should receive

 "deadline", to schedule tasks. A SCHED_DEADLINE task should receive

 "runtime" microseconds of execution time every "period" microseconds, and

 "runtime" microseconds of execution time every "period" microseconds, and

 these "runtime" microseconds are available within "deadline" microseconds

 these "runtime" microseconds are available within "deadline" microseconds
@@ -117,6 +117,10 @@ CONTENTS 
         scheduling deadline = scheduling deadline + period

         scheduling deadline = scheduling deadline + period

         remaining runtime = remaining runtime + runtime

         remaining runtime = remaining runtime + runtime





 The SCHED_FLAG_DL_OVERRUN flag in sched_attr's sched_flags field allows a task

 to get informed about runtime overruns through the delivery of SIGXCPU

 signals.







2.2 Bandwidth reclaiming

2.2 Bandwidth reclaiming

------------------------

------------------------
@@ -279,6 +283,19 @@ CONTENTS 
    running_bw is incremented.

    running_bw is incremented.









2.3 Energy-aware scheduling

------------------------



 When cpufreq's schedutil governor is selected, SCHED_DEADLINE implements the

 GRUB-PA [19] algorithm, reducing the CPU operating frequency to the minimum

 value that still allows to meet the deadlines. This behavior is currently

 implemented only for ARM architectures.



 A particular care must be taken in case the time needed for changing frequency

 is of the same order of magnitude of the reservation period. In such cases,

 setting a fixed CPU frequency results in a lower amount of deadline misses.





3. Scheduling Real-Time Tasks

3. Scheduling Real-Time Tasks

=============================

=============================
@@ -505,6 +522,12 @@ CONTENTS 
  17 - L. Abeni, G. Lipari, A. Parri, Y. Sun, Multicore CPU reclaiming: parallel

  17 - L. Abeni, G. Lipari, A. Parri, Y. Sun, Multicore CPU reclaiming: parallel

       or sequential?. In Proceedings of the 31st Annual ACM Symposium on Applied

       or sequential?. In Proceedings of the 31st Annual ACM Symposium on Applied

       Computing, 2016.

       Computing, 2016.

  18 - J. Lelli, C. Scordino, L. Abeni, D. Faggioli, Deadline scheduling in the

       Linux kernel, Software: Practice and Experience, 46(6): 821-839, June

       2016.

  19 - C. Scordino, L. Abeni, J. Lelli, Energy-Aware Real-Time Scheduling in

       the Linux Kernel, 33rd ACM/SIGAPP Symposium On Applied Computing (SAC

       2018), Pau, France, April 2018.









4. Bandwidth management

4. Bandwidth management