sigwaittest - 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]
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
- -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
- -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 <C.Emde@osadl.org>