NAME

       runqlen.bt - CPU scheduler run queue length as a histogram. Uses bpftrace/eBPF.

SYNOPSIS

       runqlen.bt

DESCRIPTION

       This program summarizes scheduler queue length as a histogram, and can also show run queue
       occupancy. It works by sampling the run queue length on all CPUs at 99 Hertz.

       This tool can be used to identify imbalances, eg, when processes are bound to CPUs causing
       queueing, or interrupt mappings causing the same.

       Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

       CONFIG_BPF and bpftrace.

EXAMPLES

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

FIELDS

       1st, 2nd
              The run queue length is shown in the first field (after "[").

       3rd    A column showing the count of samples in for that length.

       4th    This is an ASCII histogram representing the count column.

OVERHEAD

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

SOURCE

       This is from bpftrace.

              https://github.com/iovisor/bpftrace

       Also look in the bpftrace distribution  for  a  companion  _examples.txt  file  containing
       example usage, output, and commentary for this tool.

       This is a bpftrace version of the bcc tool of the same name. The bcc tool may provide more
       options and customizations.

              https://github.com/iovisor/bcc

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       runqlat(8), mpstat(1), pidstat(1), uptime(1)