NAME

funccount - Count function, tracepoint, and USDT probe calls matching a pattern. Uses Linux eBPF/bcc.

SYNOPSIS

funccount [-h] [-p PID] [-i INTERVAL] [-d DURATION] [-T] [-r] [-D] pattern

DESCRIPTION

This tool is a quick way to determine which functions are being called, and at what rate. It uses in-kernel eBPF maps to count function calls.

WARNING: This uses dynamic tracing of (what can be many) functions, an activity that has had issues on some kernel versions (risk of panics or freezes). Test, and know what you are doing, before use.

Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

CONFIG_BPF and bcc.

OPTIONS

pattern Search pattern. Supports "*" wildcards. See EXAMPLES. You can also use -r for regular expressions.

-h: Print usage message.
-p PID: Trace this process ID only.
-i INTERVAL: Print output every interval seconds.
-d DURATION: Total duration of trace in seconds.
-T: Include timestamps on output.
-r: Use regular expressions for the search pattern.
-D: Print the BPF program before starting (for debugging purposes).
-c CPU: Trace on this CPU only.

EXAMPLES

Count kernel functions beginning with "vfs_", until Ctrl-C is hit:: # funccount 'vfs_*'
Count kernel functions beginning with "tcp_send", until Ctrl-C is hit:: # funccount 'tcp_send*'
Print kernel functions beginning with "vfs_", every second:: # funccount -i 1 'vfs_*'
Print kernel functions beginning with "vfs_", for ten seconds only:: # funccount -d 10 'vfs_*'
Match kernel functions beginning with "vfs_", using regular expressions:: # funccount -r '^vfs_.*'
Count vfs calls for process ID 181 only:: # funccount -p 181 'vfs_*'
Count calls to the sched_fork tracepoint, indicating a fork() performed:: # funccount t:sched:sched_fork
Count all GC USDT probes in the Node process:: # funccount -p 185 u:node:gc*
Count all malloc() calls in libc:: # funccount c:malloc
Count kernel functions beginning with "vfs_" on CPU 1 only:: # funccount -c 1 'vfs_*'

FIELDS

FUNC: Function name
COUNT: Number of calls while tracing

OVERHEAD

This traces functions and maintains in-kernel counts, which are asynchronously copied to user-space. While the rate of calls 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. 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, Sasha Goldshtein