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JITTERDEBUGGER(1) General Commands Manual JITTERDEBUGGER(1)

NAME

jitterdebugger - measures wake up latencies

SYNOPSIS

jitterdebugger [OPTIONS]

DESCRIPTION

jitterdebugger measures wake up latencies. jitterdebugger starts a thread on each CPU which programs a timer and measures the time it takes from the timer expiring until the thread which set the timer runs again.

jitterdebugger default settings will produce a correct meassurement.

The program runs until CTRL-C or SIGTERM is received. The results are printed to STDOUT as JSON encoded string.

OPTIONS

-h, --help
Show help text and exit.
-v, --verbose
Show live updates of the measurments
-f, --file=FILE
Write the results into the FILE
-l, --loops=N
Run meassurments N times and the terminate jitterdebugger.
-b, --break=N
Run jitterdebugger until the N or greater latency has been observed. jitterdebugger will also stop a running tracer by writing 0 to tracing/tracing_on. Furthermore, the value observed will be written to the trace buffers tracing/trace_marker, e.g "Hit latency 249".
-i, --interval=N
Set the sleep time between each measuring. The default value is 1000us
-o, --output=FILE
Write all samples measured into FILE. This file is binary encoded and can be decoded using jittersamples.
-a, --affinity=CPUSET
Set the CPU affinity mask. jitterdebugger starts only meassuring threads on CPUSET,. e.g. 0,2,5-7 starts a thread on first, third and 5, 6 and 7 CPU. May also be set in hexadecimal with '0x' prefix
-p, --priority=PRI
Set the priority of the meassuring threads. The default value is 98. Note priority 99 is not available because 99 should only be used for kernel housekeeping tasks.

EXAMPLES

# jitterdebugger  -v
affinity: 0,1 = 2 [0x3]
T: 0 (  614) A: 0 C:     13476 Min:         3 Avg:    3.08 Max:        10
T: 1 (  615) A: 1 C:     13513 Min:         3 Avg:    3.10 Max:        20
^C
{
  "cpu": {
    "0": {
      "histogram": {
        "3": 4070,
        "4": 269,
        "5": 26,
        "6": 5,
        "7": 1,
        "8": 1,
        "9": 2,
        "10": 1
      },
      "count": 4375,
      "min": 3,
      "max": 10,
      "avg": 3.08
    },
    "1": {
      "histogram": {
        "3": 4002,
        "4": 320,
        "5": 22,
        "6": 4,
        "7": 2,
        "8": 1,
        "10": 2,
        "11": 1,
        "16": 2,
        "20": 1
      },
      "count": 4357,
      "min": 3,
      "max": 20,
      "avg": 3.10
    }
  }
}

SEE ALSO

jittersamples(1) jitterplot(1)