DOKK / manpages / debian 11 / rt-tests / svsematest.8.en
svsematest(8) svsematest(8)

svsematest - Start two threads or fork two processes and measure the latency of SYSV semaphores

svsematest [-a|-a PROC] [-b USEC] [-d DIST] [-f] [-i INTV] [-l loops] [-p PRIO] [-t|-t NUM]

The program svsematest starts two threads or, optionally, forks two processes that are synchronized via SYSV semaphores and measures the latency between releasing a semaphore on one side and getting it on the other side.

Run on processor number PROC. If PROC is not specified, run on current processor.
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.
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
Specify a length for the test run.
Append 'm', 'h', or 'd' to specify minutes, hours or days.
Instead of creating threads (which is the default), fork new processes
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.
Set the number of loops. The default is 0 (endless). This option is useful for automated tests with a given number of test cycles. svsematest is stopped once the number of timer intervals has been reached.
Set the priority of the process.
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:

# svsematest -a -t -p99 -i100 -d25 -l1000000
#0: ID13110, P99, CPU0, I100; #1: ID13111, P99, CPU0, Cycles 1000000
#2: ID13112, P98, CPU1, I125; #3: ID13113, P98, CPU1, Cycles 813573
#4: ID13114, P97, CPU2, I150; #5: ID13115, P97, CPU2, Cycles 667285
#6: ID13116, P96, CPU3, I175; #7: ID13117, P96, CPU3, Cycles 591403
#1 -> #0, Min    1, Cur    2, Avg    2, Max   12
#3 -> #2, Min    1, Cur    3, Avg    2, Max   12
#5 -> #4, Min    1, Cur    3, Avg    3, Max   12
#7 -> #6, Min    1, Cur    2, Avg    3, Max   11

Carsten Emde <C.Emde@osadl.org>

semop(2)

0.1