NAME

hardirqs - Measure hard IRQ (hard interrupt) event time. Uses Linux eBPF/bcc.

SYNOPSIS

hardirqs [-h] [-T] [-N] [-C] [-d] [interval] [outputs]

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.

REQUIREMENTS

CONFIG_BPF and bcc.

OPTIONS

-h: Print usage message.
-T: Include timestamps on output.
-N: Output in nanoseconds.
-C: Count events only.
-d: Show IRQ time distribution as histograms.
-c CPU: Trace on this CPU only.

EXAMPLES

Sum hard IRQ event time until Ctrl-C:: # hardirqs
Show hard IRQ event time as histograms:: # hardirqs -d
Print 1 second summaries, 10 times:: # hardirqs 1 10
1 second summaries, printed in nanoseconds, with timestamps:: # hardirqs -NT 1
Sum hard IRQ event time on CPU 1 until Ctrl-C:: # hardirqs -c 1

FIELDS

HARDIRQ: The irq action name for this hard IRQ.
TOTAL_usecs: Total time spent in this hard IRQ in microseconds.
TOTAL_nsecs: Total time spent in this hard IRQ in nanoseconds.
usecs: Range of microseconds for this bucket.
nsecs: Range of nanoseconds for this bucket.
count: Number of hard IRQs in this time range.
distribution: ASCII representation of the distribution (the count column).

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.

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, Hengqi Chen, Rocky Xing