[PATCH 4/4] Documentation/scheduler/sched-deadline.txt: add tests suite appendix

From: Juri Lelli
Date: Tue Aug 12 2014 - 11:51:01 EST

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@xxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Henrik Austad <henrik@xxxxxxxxx>
Cc: Dario Faggioli <raistlin@xxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Documentation/scheduler/sched-deadline.txt | 52 ++++++++++++++++++++++++++++
1 file changed, 52 insertions(+)

diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt
index d056034..52eb25f 100644
--- a/Documentation/scheduler/sched-deadline.txt
+++ b/Documentation/scheduler/sched-deadline.txt
@@ -15,6 +15,7 @@ CONTENTS
5. Tasks CPU affinity
5.1 SCHED_DEADLINE and cpusets HOWTO
6. Future plans
+ A. Test suite

@@ -339,3 +340,54 @@ 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.
+ Threads parameters can be specified from command line, with something like
+ this:
+ # rt-app -t 100000:10000:d -t 150000:20000:f:10 -D5
+ What above creates two threads, first one, scheduled by SCHED_DEADLINE,
+ executes for 10ms every 100ms and second one, scheduled at RT priority 10
+ with SCHED_FIFO, executes for 20ms every 150ms. The configuration runs
+ for 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.
+ 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

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