softirqs-bpfcc(8)

Usage

softirqs [-h] [-T] [-N] [-C] [-d] [-c CPU] [interval] [count]

Overview

This summarizes the time spent servicing soft IRQs (soft interrupts), and can show this time as either totals or histogram distributions. A system-wide summary of this time is shown by the %soft column of mpstat(1), and soft IRQ event counts (but not times) are available in /proc/softirqs.

This tool uses the irq:softirq_enter and irq:softirq_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: Show the number of soft irq events.

-d: Show IRQ time distribution as histograms.

-c CPU: Trace on this CPU only.

Examples

`Sum soft IRQ event time until Ctrl-C:`	# `softirqs`
`Show the number of soft irq events:`	# softirqs -C
`Show soft IRQ event time as histograms:`	# softirqs -d
`Print 1 second summaries, 10 times:`	# softirqs 1 10
`1 second summaries, printed in nanoseconds, with timestamps:`	# softirqs -NT 1
`Sum soft IRQ event time on CPU 1 until Ctrl-C:`	# softirqs -c 1

Fields

`SOFTIRQ`	The kernel function name that performs the soft IRQ action.
`TOTAL_usecs`	Total time spent in this soft IRQ function in microseconds.
`TOTAL_nsecs`	Total time spent in this soft IRQ function in nanoseconds.
`usecs`	Range of microseconds for this bucket.
`nsecs`	Range of nanoseconds for this bucket.
`count`	Number of soft 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.

Releases

4 releases since Debian 10 (Buster); the text changed 1 time.

-C since Debian 12 (Bookworm); -c since Debian 12 (Bookworm).