Your company here — click to reach over 10,000 unique daily visitors

sigwaittest - Man Page

Start two threads or fork two processes and measure the latency between sending and receiving a signal

# SPDX-License-Identifier: GPL-2.0-only


sigwaittest [-a|--affinity PROC] [-b|--breaktrace USEC] [-d|--distance DIST] [-D|--duration TIME] [-f|--fork [OPT]] [-i|--interval INTV] [--json FILENAME] [-l|--loops LOOPS] [-p|--prio PRIO] [-t|--threads [NUM]]


The program sigwaittest starts two threads or, optionally, forks two processes that are synchronized via signals and measures the latency between sending a signal and returning from sigwait().


-a,  --affinity[=PROC]

Run on processor number PROC. If PROC is not specified, run on current processor.

-b,  --breaktrace=USEC

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 of a system.

-d,  --distance=DIST

Set the distance of thread intervals in microseconds (default is 500 us). 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

-D,  --duration=TIME

Specify a length for the test run.
Append 'm', 'h', or 'd' to specify minutes, hours or days.

-f,  --fork[=OPT]

Instead of creating threads (which is the default), fork new processes

-i,  --interval=INTV

Set the base interval of the thread(s) in microseconds (default is 1000 us). This sets the interval of the first thread. See also -d.


Write final results into FILENAME, JSON formatted.

-l,  --loops=LOOPS

Set the number of loops. The default is 0 (endless). This option is useful for automated tests with a given number of test cycles. sigwaittest is stopped once the number of timer intervals has been reached.

-p,  --prio=PRIO

Set the priority of the process.

-t,  --threads[=NUM]

Set the number of test threads (default is 1, if this option is not given). If NUM is specified, create NUM test threads. If NUM is not specified, NUM is set to the number of available CPUs.


The following example was running on a 4-way CPU:

# sigwaittest -a -t -p99 -i100 -d25 -l1000000
#0: ID11510, P99, CPU0, I100; #1: ID11511, P99, CPU0, Cycles 1000000
#2: ID11512, P98, CPU1, I125; #3: ID11513, P98, CPU1, Cycles 817484
#4: ID11514, P97, CPU2, I150; #5: ID11515, P97, CPU2, Cycles 668213
#6: ID11516, P96, CPU3, I175; #7: ID11517, P96, CPU3, Cycles 597344
#1 -> #0, Min    1, Cur    2, Avg    3, Max   30
#3 -> #2, Min    1, Cur   26, Avg    3, Max   42
#5 -> #4, Min    1, Cur   46, Avg    4, Max   67
#7 -> #6, Min    1, Cur    2, Avg    3, Max   74


Carsten Emde <C.Emde@osadl.org>

See Also

kill(2), sigwait(3)