preemptirq_delay_test: Add the burst feature and a sysfs trigger
authorViktor Rosendahl (BMW) <viktor.rosendahl@gmail.com>
Tue, 8 Oct 2019 22:08:22 +0000 (00:08 +0200)
committerSteven Rostedt (VMware) <rostedt@goodmis.org>
Wed, 13 Nov 2019 14:37:28 +0000 (09:37 -0500)
commit793937236d1ee032d2ee5ccc27bdd280a04e766e
treee3662d9c0f5dbfc0fc8663af5a33622ff9dda763
parent91edde2e6ae1dd5e33812f076f3fe4cb7ccbfdd0
preemptirq_delay_test: Add the burst feature and a sysfs trigger

This burst feature enables the user to generate a burst of
preempt/irqsoff latencies. This makes it possible to test whether we
are able to detect latencies that systematically occur very close to
each other.

The maximum burst size is 10. We also create 10 identical test
functions, so that we get 10 different backtraces; this is useful
when we want to test whether we can detect all the latencies in a
burst. Otherwise, there would be no easy way of differentiating
between which latency in a burst was captured by the tracer.

In addition, there is a sysfs trigger, so that it's not necessary to
reload the module to repeat the test. The trigger will appear as
/sys/kernel/preemptirq_delay_test/trigger in sysfs.

Link: http://lkml.kernel.org/r/20191008220824.7911-3-viktor.rosendahl@gmail.com
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Viktor Rosendahl (BMW) <viktor.rosendahl@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
kernel/trace/Kconfig
kernel/trace/preemptirq_delay_test.c