.TH hardirqs 8  "2015-10-20" "USER COMMANDS"
.SH NAME
hardirqs \- Measure hard IRQ (hard interrupt) event time. Uses Linux eBPF/bcc.
.SH SYNOPSIS
.B hardirqs [\-h] [\-T] [\-N] [\-C] [\-d] [interval] [outputs]
.SH DESCRIPTION
This summarizes the time spent servicing hard IRQs (hard interrupts), and can
show this time as either totals or histogram distributions. A system-wide
summary of this time is shown by the %irq column of mpstat(1), and event
counts (but not times) are shown by /proc/interrupts.

This tool uses the irq:irq_handler_entry and irq:irq_handler_exit kernel
tracepoints, which is a stable tracing mechanism. BPF programs can attach to
tracepoints from Linux 4.7 only. An older version of this tool is available
in tools/old, and uses kprobes instead of tracepoints.

Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF and bcc.
.SH OPTIONS
.TP
\-h
Print usage message.
.TP
\-T
Include timestamps on output.
.TP
\-N
Output in nanoseconds.
.TP
\-C
Count events only.
.TP
\-d
Show IRQ time distribution as histograms.
.TP
\-c CPU
Trace on this CPU only.
.SH EXAMPLES
.TP
Sum hard IRQ event time until Ctrl-C:
#
.B hardirqs
.TP
Show hard IRQ event time as histograms:
#
.B hardirqs \-d
.TP
Print 1 second summaries, 10 times:
#
.B hardirqs 1 10
.TP
1 second summaries, printed in nanoseconds, with timestamps:
#
.B hardirqs \-NT 1
.TP
Sum hard IRQ event time on CPU 1 until Ctrl-C:
#
.B hardirqs \-c 1
.SH FIELDS
.TP
HARDIRQ
The irq action name for this hard IRQ.
.TP
TOTAL_usecs
Total time spent in this hard IRQ in microseconds.
.TP
TOTAL_nsecs
Total time spent in this hard IRQ in nanoseconds.
.TP
usecs
Range of microseconds for this bucket.
.TP
nsecs
Range of nanoseconds for this bucket.
.TP
count
Number of hard IRQs in this time range.
.TP
distribution
ASCII representation of the distribution (the count column).
.SH OVERHEAD
This traces kernel functions and maintains in-kernel counts, which
are asynchronously copied to user-space. While the rate of interrupts
be very high (>1M/sec), this is a relatively efficient way to trace these
events, and so the overhead is expected to be small for normal workloads, but
could become noticeable for heavy workloads. Measure in a test environment
before use.
.SH SOURCE
This is from bcc.
.IP
https://github.com/iovisor/bcc
.PP
Also look in the bcc distribution for a companion _examples.txt file containing
example usage, output, and commentary for this tool.
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHOR
Brendan Gregg, Hengqi Chen, Rocky Xing
.SH SEE ALSO
softirqs(8)