NAME

softirqs - Measure soft IRQ (soft interrupt) event time. Uses Linux eBPF/bcc.

SYNOPSIS

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

DESCRIPTION

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.

AUTHORS

Brendan Gregg, Sasha Goldshtein, Rocky Xing