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Commit bb4e30a4 authored by Claudio Scordino's avatar Claudio Scordino Committed by Ingo Molnar
Browse files

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 Diff line number Diff line
@@ -49,7 +49,7 @@ CONTENTS 
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

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

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

         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

------------------------
@@ -279,6 +283,19 @@ CONTENTS 
    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

=============================
@@ -505,6 +522,12 @@ CONTENTS 
  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

       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