softirqs(8) System Manager's Manual softirqs(8)
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 mp-
stat(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 trace-
points, 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 work-
loads, 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
SEE ALSO
hardirqs(8)
USER COMMANDS 2015-10-20 softirqs(8)
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