High resolution test program
cyclictest [ -hfmnqrsvMS ] [-a proc ] [-A align ] [-b usec ] [-c clock ] [-d dist ] [-h histogram ] [-i intv ] [-l loop ] [-o red ] [-p prio ] [-t num ] [-D time] [-w] [-W] [-y policy ] [ -S | -U ]
These programs follow the usual GNU command line syntax, with long options starting with two dashes ('--').
A summary of options is included below.
Run threads on the set of procesors given by PROC-SET. If PROC-SET is not specified, all processors will be used. Threads will be assigned to processors in the set in numeric order, in a round-robin fashion.
The set of processors can be specified as A,B,C, or A-C, or A-B,D-F, and so on*. The ! character can be used to negate a set. For example, !B-D means to use all available CPUs except B through D. The cpu numbers are the same as shown in the processor field in /proc/cpuinfo. See numa(3) for more information on specifying CPU sets. * Support for CPU sets requires libnuma version >= 2. For libnuma v1, PROC-SET, if specified, must be a single CPU number.
Align measurement thread wakeups to a specific offset in microseconds
Send break trace command when latency > USEC. This is a debugging option to control the latency tracer in the realtime preemption patch. It is useful to track down unexpected large latencies on a system. This option does only work with following kernel config options.
For kernel < 2.6.24:
For kernel >= 2.6.24:
kernel configuration options enabled. The USEC parameter to the -b option defines a maximum latency value, which is compared against the actual latencies of the test. Once the measured latency is higher than the given maximum, the kernel tracer and cyclictest is stopped. The trace can be read from /proc/latency_trace. Please be aware that the tracer adds significant overhead to the kernel, so the latencies will be much higher than on a kernel with latency tracing disabled.
Selects the clock, which is used:
* 0 selects CLOCK_MONOTONIC, which is the monotonic increasing system time (default). * 1 selects CLOCK_REALTIME, which is the time of day time.
CLOCK_REALTIME can be set by settimeofday, while CLOCK_MONOTONIC can not be modified by the user. This option has no influence when the -s option is given.
context switch tracing (used with -b)
Set the distance of thread intervals in microseconds (default is 500us). When cyclictest is called with the -t option and more than one thread is created, then this distance value is added to the interval of the threads: Interval(thread N) = Interval(thread N-1) + DIST
event tracing (used with -b)
Enable function tracing using ftrace as tracer. This option is available only with -b.
Dump latency histogram to stdout. US means the max time to be be tracked in microseconds. When you use -h option to get histogram data, Cyclictest runs many threads with same priority without priority--.
Same as -h except that an additional histogram column is displayed at the right that contains summary data of all thread histograms. If cyclictest runs a single thread only, the -H option is equivalent to -h.
Set the base interval of the thread(s) in microseconds (default is 1000us). This sets the interval of the first thread. See also -d.
Set the number of loops. The default is 0 (endless). This option is useful for automated tests with a given number of test cycles. Cyclictest is stopped once the number of timer intervals has been reached.
Use clock_nanosleep instead of posix interval timers. Setting this option runs the tests with clock_nanosleep instead of posix interval timers.
Show results in nanoseconds instead of microseconds, which is the default unit.
Oscilloscope mode, reduce verbose output by RED.
Used to pass tracing options to ftrace tracers. May be invoked mutiple times for multiple trace options. For example trace options look at /sys/kernel/debug/tracing/trace_options
Set the priority of the first thread. The given priority is set to the first test thread. Each further thread gets a lower priority: Priority(Thread N) = max(Priority(Thread N-1) - 1, 0)
Run the tests quiet and print only a summary on exit. Useful for automated tests, where only the summary output needs to be captured.
Use relative timers instead of absolute. The default behaviour of the tests is to use absolute timers. This option is there for completeness and should not be used for reproducible tests.
Use sys_nanosleep and sys_setitimer instead of posix timers. Note, that -s can only be used with one thread because itimers are per process and not per thread. -s in combination with -n uses the nanosleep syscall and is not restricted to one thread.
set the ftrace tracer function. Used with the -b option. Must be one of the trace functions available from <debugfs-mountpoint>/kernel/debug/tracing/available_tracers
Set the number of test threads (default is 1). Create NUM test threads. If NUM is not specified, NUM is set to the number of available CPUs. See -d, -i and -p for further information.
Lock current and future memory allocations to prevent being paged out
Output values on stdout for statistics. This option is used to gather statistical information about the latency distribution. The output is sent to stdout. The output format is:
where n=task number c=count v=latency value in us. Use this option in combination with -l
Run the test for the specified time, which defaults to seconds. Append 'm', 'h', or 'd' to specify minutes, hours or days
task wakeup tracing (used with -b)
rt-task wakeup tracing (used with -b)
set the scheduler policy of the measurement threads where NAME is one of: other, normal, batch, idle, fifo, rr
delay updating the screen until a new max latency is hit (useful for running cyclictest on low-bandwidth connections)
Set options for standard testing on SMP systems. Equivalent to using the options: "-t -a -n" as well keeping any specified priority equal across all threads
Similar to the above --smp option, this implies the "-t -a -n" options, as well as a constant measurement interval, but also forces memory allocations using the numa(3) policy library. Thread stacks and data structures are allocated from the NUMA node local to the core to which the thread is bound. Requires the underlying kernel to have NUMA support compiled in.
cyclictest was written by Thomas Gleixner <[email protected]>.
This manual page was written by Alessio Igor Bogani <[email protected]>, for the Debian project (but may be used by others).