runqlen(8) System Manager's Manual runqlen(8)
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 sepa-
rately:
# runqlen -CT 1
Print run queue occupancy every second:
# runqlen -O 1
Print run queue occupancy, with timestamps, for each CPU:
# runqlen -COT 1
FIELDS
runqlen
Scheduler run queue length: the number of threads (tasks) wait-
ing 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), runqslower(8), pidstat(1)
USER COMMANDS 2016-12-12 runqlen(8)
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