NAME

       runqlen - Scheduler run queue length as a histogram.

SYNOPSIS

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

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 bcc.

OPTIONS

       -h     Print usage message.

       -T     Include timestamps on output.

       -O     Report run queue occupancy.

       -C     Report for each CPU.

       interval
              Output interval, in seconds.

       count  Number of outputs.

EXAMPLES

       Summarize run queue length as a histogram:
              # runqlen

       Print 1 second summaries, 10 times:
              # runqlen 1 10

       Print output every second, with timestamps, and show each CPU separately:
              # runqlen -CT 1

       Print run queue occupancy every second:
              # runqlen -O 1

       Print run queue occupancy, with timetamps, for each CPU:
              # runqlen -COT 1

FIELDS

       runqlen
              Scheduler  run  queue  length:  the  number  of  threads  (tasks)  waiting  to run,
              (excluding including the currently running task).

       count  Number of samples at this queue length.

       distribution
              An ASCII bar chart to visualize the distribution (count column)

OVERHEAD

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

SOURCE

       This is from bcc.

              https://github.com/iovisor/bcc

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

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       runqlat(8), pidstat(1)