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Commit f5801933 authored by Juri Lelli's avatar Juri Lelli Committed by Ingo Molnar
Browse files

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



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: default avatarJuri Lelli <juri.lelli@arm.com>
Reviewed-by: default avatarHenrik 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: default avatarIngo Molnar <mingo@kernel.org>
parent b56bfc6c

Documentation/scheduler/sched-deadline.txt

+52 −0
Original line number Diff line number Diff line
@@ -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