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)