NAME

       funccount - count kernel function calls matching specified wildcards. Uses Linux ftrace.

SYNOPSIS

       funccount [-hT] [-i secs] [-d secs] [-t top] funcstring

DESCRIPTION

       This tool is a quick way to determine which kernel functions are being called, and at what
       rate. It uses ftrace function profiling capabilities.

       WARNING: This uses dynamic tracing of (what can be many) kernel functions, and could cause
       kernel panics or freezes. Test, and know what you are doing, before use.

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

REQUIREMENTS

       CONFIG_FUNCTION_PROFILER,  which  you  may  already  have  enabled and available on recent
       kernels, and awk.

OPTIONS

       -d seconds Total duration of the trace.

       -h     Print usage message.

       -i seconds
              Print an interval summary every so many seconds.

       -t top Print top number of entries only.

       -T     Include timestamp on each summary.

       funcstring
              A function name to trace, which may include file glob style wildcards ("*") at  the
              beginning  or  ending  of  a  string only. Eg, "vfs*" means match "vfs" followed by
              anything.

EXAMPLES

       Count every kernel function beginning with "bio_", until Ctrl-C is hit:
              # funccount 'bio_*'

       Count every "tcp_*" kernel function, and print a summary every one second, five in total:
              # funccount -i 1 -d 5 'tcp_*'

       Count every "ext4*" kernel function, and print the top 20 when Ctrl-C is hit:
              # funccount -t 20 'ext4*'

FIELDS

       FUNC   Kernel function name.

       COUNT  Number of times this function was called during the tracing interval.

OVERHEAD

       This uses the ftrace profiling  framework,  which  does  in-kernel  counts,  lowering  the
       overhead (compared to tracing each event).

SOURCE

       This is from the perf-tools collection:

              https://github.com/brendangregg/perf-tools

       Also  look  under the examples directory for a text file containing example usage, output,
       and commentary for this tool.

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       functrace(8)