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sched/deadline/Documentation: Add overrun signal and GRUB-PA documentation

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Signed-off-by: Claudio Scordino <claudio@evidence.eu.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Claudio Scordino 2018-04-03 09:42:42 +02:00 committed by Ingo Molnar
parent 943d355d7f
commit bb4e30a480
1 changed files with 24 additions and 1 deletions

25
Documentation/scheduler/sched-deadline.txt

@ -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