Manual: runqlen.bt

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

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 over‐
       head of this tool is expected to be near zero.

SOURCE
       This is from bpftrace.

	      https://github.com/bpftrace/bpftrace

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

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

	      https://github.com/iovisor/bcc

OS
       Linux

STABILITY
       Unstable - in development.

AUTHOR
       Brendan Gregg

SEE ALSO
       runqlat.bt(8), mpstat(1), pidstat(1), uptime(1)

USER COMMANDS						 2018-10-07					       runqlen.bt(8)