1svsematest(8) svsematest(8)
2# SPDX-License-Identifier: GPL-2.0-or-later
6
8 svsematest - Start two threads or fork two processes and measure the
9 latency of SYSV semaphores
10
12 svsematest [-a|--affinity NUM] [-b|--breaktrace USEC] [-d|--distance
13 DIST] [-D|--duration TIME] [-f|--fork [OPT]] [-i|--interval INTV]
14 [--json FILENAME] [-l|--loops LOOPS] [-p|--prio PRIO] [-q|--quiet]
15 [-S|--smp] [-t|--threads [NUM]]
16
18 The program svsematest starts two threads or, optionally, forks two
19 processes that are synchronized via SYSV semaphores and measures the
20 latency between releasing a semaphore on one side and getting it on the
21 other side.
22
24 -a, --affinity[=NUM]
25 Run on processor number NUM. If PROC is not specified, run on
26 current processor.
27 -b, --breaktrace=USEC
29 Send break trace command when latency > USEC. This is a debug‐
30 ging option to control the latency tracer in the realtime pre‐
31 emption patch. It is useful to track down unexpected large la‐
32 tencies of a system.
33 -d, --distance=DIST
35 Set the distance of thread intervals in microseconds (default is
36 500 us). When cyclictest is called with the -t option and more
37 than one thread is created, then this distance value is added to
38 the interval of the threads: Interval(thread N) = Inter‐
39 val(thread N-1) + DIST
40 -D, --duration=TIME
42 Specify a length for the test run.
43 Append 'm', 'h', or 'd' to specify minutes, hours or days.
44 -f, --fork
46 Instead of creating threads (which is the default), fork new
47 processes
48 -i, --interval=INTV
50 Set the base interval of the thread(s) in microseconds (default
51 is 1000 us). This sets the interval of the first thread. See
52 also -d.
53 --json=FILENAME
55 Write final results into FILENAME, JSON formatted.
56 -l, --loops=LOOPS
58 Set the number of loops. The default is 0 (endless). This option
59 is useful for automated tests with a given number of test cy‐
60 cles. svsematest is stopped once the number of timer intervals
61 has been reached.
62 -p, --prio=PRIO
64 Set the priority of the process.
65 -q, --quiet
67 Print a summary only on exit. Useful for automated tests, where
68 only the summary output needs to be captured.
69 -S, --smp
71 SMP testing: options -a -t and same priority of all threads
72 -t, --threads[=NUM]
74 Set the number of test threads (default is 1, if this option is
75 not given). If NUM is specified, create NUM test threads. If NUM
76 is not specified, NUM is set to the number of available CPUs.
77
79 The following example was running on a 4-way CPU:
80 # svsematest -a -t -p99 -i100 -d25 -l1000000
82 #0: ID13110, P99, CPU0, I100; #1: ID13111, P99, CPU0, Cycles 1000000
83 #2: ID13112, P98, CPU1, I125; #3: ID13113, P98, CPU1, Cycles 813573
84 #4: ID13114, P97, CPU2, I150; #5: ID13115, P97, CPU2, Cycles 667285
85 #6: ID13116, P96, CPU3, I175; #7: ID13117, P96, CPU3, Cycles 591403
86 #1 -> #0, Min 1, Cur 2, Avg 2, Max 12
87 #3 -> #2, Min 1, Cur 3, Avg 2, Max 12
88 #5 -> #4, Min 1, Cur 3, Avg 3, Max 12
89 #7 -> #6, Min 1, Cur 2, Avg 3, Max 11
90
92 Carsten Emde <C.Emde@osadl.org>
93
95 semop(2)
96 0.1 svsematest(8)