bcc-runqlen(8)

1runqlen(8)                  System Manager's Manual                 runqlen(8)
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NAME

6       runqlen - Scheduler run queue length as a histogram.
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SYNOPSIS

9       runqlen [-h] [-T] [-O] [-C] [interval] [count]
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DESCRIPTION

12       This  program summarizes scheduler queue length as a histogram, and can
13       also show run queue occupancy. It  works  by  sampling  the  run  queue
14       length on all CPUs at 99 Hertz.
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16       This  tool  can  be used to identify imbalances, eg, when processes are
17       bound to CPUs causing queueing, or interrupt mappings causing the same.
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19       Since this uses BPF, only the root user can use this tool.
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REQUIREMENTS

22       CONFIG_BPF and bcc.
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OPTIONS

25       -h     Print usage message.
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27       -T     Include timestamps on output.
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29       -O     Report run queue occupancy.
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31       -C     Report for each CPU.
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33       interval
34              Output interval, in seconds.
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36       count  Number of outputs.
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EXAMPLES

39       Summarize run queue length as a histogram:
40              # runqlen
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42       Print 1 second summaries, 10 times:
43              # runqlen 1 10
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45       Print output every second, with timestamps, and  show  each  CPU  sepa‐
46       rately:
47              # runqlen -CT 1
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49       Print run queue occupancy every second:
50              # runqlen -O 1
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52       Print run queue occupancy, with timetamps, for each CPU:
53              # runqlen -COT 1
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FIELDS

56       runqlen
57              Scheduler  run queue length: the number of threads (tasks) wait‐
58              ing to run, (excluding including the currently running task).
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60       count  Number of samples at this queue length.
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62       distribution
63              An ASCII bar chart to visualize the distribution (count column)
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OVERHEAD

66       This uses sampling at 99 Hertz (on all CPUs), and in-kernel  summaries,
67       which  should  make  overhead negligible. This does not trace scheduler
68       events, like runqlen does, which comes at a much higher overhead cost.
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SOURCE

71       This is from bcc.
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73              https://github.com/iovisor/bcc
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75       Also look in the bcc distribution for a  companion  _examples.txt  file
76       containing example usage, output, and commentary for this tool.
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OS

79       Linux
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STABILITY

82       Unstable - in development.
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AUTHOR

85       Brendan Gregg
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