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Documentation/scheduler/sched-deadline.txt: Add tests suite appendix

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Add an appendix briefly describing tools that can be used to
test SCHED_DEADLINE (and the scheduler in general). Links to
where source code of the tools is hosted are also provided.

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Reviewed-by: Henrik Austad <henrik@austad.us>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dario Faggioli <raistlin@linux.it>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1410256636-26171-5-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Juri Lelli 2014-09-09 10:57:15 +01:00 committed by Ingo Molnar
parent b56bfc6cd1
commit f5801933ce
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Documentation/scheduler/sched-deadline.txt
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@ -15,6 +15,7 @@ CONTENTS
5. Tasks CPU affinity
5.1 SCHED_DEADLINE and cpusets HOWTO
6. Future plans
A. Test suite
0. WARNING
@ -345,3 +346,54 @@ CONTENTS
throttling patches [https://lkml.org/lkml/2010/2/23/239] but we still are in
the preliminary phases of the merge and we really seek feedback that would
help us decide on the direction it should take.
Appendix A. Test suite
======================
The SCHED_DEADLINE policy can be easily tested using two applications that
are part of a wider Linux Scheduler validation suite. The suite is
available as a GitHub repository: https://github.com/scheduler-tools.
The first testing application is called rt-app and can be used to
start multiple threads with specific parameters. rt-app supports
SCHED_{OTHER,FIFO,RR,DEADLINE} scheduling policies and their related
parameters (e.g., niceness, priority, runtime/deadline/period). rt-app
is a valuable tool, as it can be used to synthetically recreate certain
workloads (maybe mimicking real use-cases) and evaluate how the scheduler
behaves under such workloads. In this way, results are easily reproducible.
rt-app is available at: https://github.com/scheduler-tools/rt-app.
Thread parameters can be specified from the command line, with something like
this:
# rt-app -t 100000:10000:d -t 150000:20000:f:10 -D5
The above creates 2 threads. The first one, scheduled by SCHED_DEADLINE,
executes for 10ms every 100ms. The second one, scheduled at SCHED_FIFO
priority 10, executes for 20ms every 150ms. The test will run for a total
of 5 seconds.
More interestingly, configurations can be described with a json file that
can be passed as input to rt-app with something like this:
# rt-app my_config.json
The parameters that can be specified with the second method are a superset
of the command line options. Please refer to rt-app documentation for more
details (<rt-app-sources>/doc/*.json).
The second testing application is a modification of schedtool, called
schedtool-dl, which can be used to setup SCHED_DEADLINE parameters for a
certain pid/application. schedtool-dl is available at:
https://github.com/scheduler-tools/schedtool-dl.git.
The usage is straightforward:
# schedtool -E -t 10000000:100000000 -e ./my_cpuhog_app
With this, my_cpuhog_app is put to run inside a SCHED_DEADLINE reservation
of 10ms every 100ms (note that parameters are expressed in microseconds).
You can also use schedtool to create a reservation for an already running
application, given that you know its pid:
# schedtool -E -t 10000000:100000000 my_app_pid