sigwaittest(8) Start two threads or fork two processes and measure the latency between sending and receiving a signal


sigwaittest [-a|-a PROC] [-b USEC] [-d DIST] [-f] [-i INTV] [-l loops] [-p PRIO] [-t|-t 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
-f, --fork
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.
-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 <[email protected]>