runqlen.bt(8)

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

6       runqlen.bt  -  CPU scheduler run queue length as a histogram. Uses bpf‐
7       trace/eBPF.
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SYNOPSIS

10       runqlen.bt
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DESCRIPTION

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

23       CONFIG_BPF and bpftrace.
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EXAMPLES

26       Trace CPU run queue length system wide, printing a histogram on Ctrl-C:
27              # runqlen.bt
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FIELDS

30       1st, 2nd
31              The run queue length is shown in the first field (after "[").
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33       3rd    A column showing the count of samples in for that length.
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35       4th    This is an ASCII histogram representing the count column.
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OVERHEAD

38       This samples scheduler structs at 99 Hertz across all CPUs. Relatively,
39       this is a low rate of events, and the overhead of this tool is expected
40       to be near zero.
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SOURCE

43       This is from bpftrace.
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45              https://github.com/iovisor/bpftrace
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47       Also  look  in  the bpftrace distribution for a companion _examples.txt
48       file containing example usage, output, and commentary for this tool.
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50       This is a bpftrace version of the bcc tool of the same  name.  The  bcc
51       tool may provide more options and customizations.
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53              https://github.com/iovisor/bcc
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OS

56       Linux
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STABILITY

59       Unstable - in development.
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AUTHOR

62       Brendan Gregg
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