NAME

       readprofile - read kernel profiling information

SYNOPSIS

       readprofile [options]

VERSION

       This manpage documents version 2.0 of the program.

DESCRIPTION

       The readprofile command uses the /proc/profile information to print ascii data on standard output. The
       output is organized in three columns: the first is the number of clock ticks, the second is the name of
       the C function in the kernel where those many ticks occurred, and the third is the normalized `load' of
       the procedure, calculated as a ratio between the number of ticks and the length of the procedure. The
       output is filled with blanks to ease readability.

OPTIONS

       -a, --all
           Print all symbols in the mapfile. By default the procedures with reported ticks are not printed.

       -b, --histbin
           Print individual histogram-bin counts.

       -i, --info
           Info. This makes readprofile only print the profiling step used by the kernel. The profiling step is
           the resolution of the profiling buffer, and is chosen during kernel configuration (through make
           config), or in the kernel’s command line. If the -t (terse) switch is used together with -i only the
           decimal number is printed.

       -m, --mapfile mapfile
           Specify a mapfile, which by default is /usr/src/linux/System.map. You should specify the map file on
           cmdline if your current kernel isn’t the last one you compiled, or if you keep System.map elsewhere.
           If the name of the map file ends with .gz it is decompressed on the fly.

       -M, --multiplier multiplier
           On some architectures it is possible to alter the frequency at which the kernel delivers profiling
           interrupts to each CPU. This option allows you to set the frequency, as a multiplier of the system
           clock frequency, HZ. Linux 2.6.16 dropped multiplier support for most systems. This option also
           resets the profiling buffer, and requires superuser privileges.

       -p, --profile pro-file
           Specify a different profiling buffer, which by default is /proc/profile. Using a different pro-file
           is useful if you want to `freeze' the kernel profiling at some time and read it later. The
           /proc/profile file can be copied using cat(1) or cp(1). There is no more support for compressed
           profile buffers, like in readprofile-1.1, because the program needs to know the size of the buffer in
           advance.

       -r, --reset
           Reset the profiling buffer. This can only be invoked by root, because /proc/profile is readable by
           everybody but writable only by the superuser. However, you can make readprofile set-user-ID 0, in
           order to reset the buffer without gaining privileges.

       -s, --counters
           Print individual counters within functions.

       -v, --verbose
           Verbose. The output is organized in four columns and filled with blanks. The first column is the RAM
           address of a kernel function, the second is the name of the function, the third is the number of
           clock ticks and the last is the normalized load.

       -h, --help
           Display help text and exit.

       -V, --version
           Print version and exit.

FILES

       /proc/profile
           A binary snapshot of the profiling buffer.

       /usr/src/linux/System.map
           The symbol table for the kernel.

       /usr/src/linux/*
           The program being profiled :-)

BUGS

       readprofile only works with a 1.3.x or newer kernel, because /proc/profile changed in the step from 1.2
       to 1.3.

       This program only works with ELF kernels. The change for a.out kernels is trivial, and left as an
       exercise to the a.out user.

       To enable profiling, the kernel must be rebooted, because no profiling module is available, and it
       wouldn’t be easy to build. To enable profiling, you can specify profile=2 (or another number) on the
       kernel commandline. The number you specify is the two-exponent used as profiling step.

       Profiling is disabled when interrupts are inhibited. This means that many profiling ticks happen when
       interrupts are re-enabled. Watch out for misleading information.

EXAMPLE

       Browse the profiling buffer ordering by clock ticks:

              readprofile | sort -nr | less

       Print the 20 most loaded procedures:

              readprofile | sort -nr +2 | head -20

       Print only filesystem profile:

              readprofile | grep _ext2

       Look at all the kernel information, with ram addresses:

              readprofile -av | less

       Browse a 'frozen' profile buffer for a non current kernel:

              readprofile -p ~/profile.freeze -m /zImage.map.gz

       Request profiling at 2kHz per CPU, and reset the profiling buffer:

              sudo readprofile -M 20

REPORTING BUGS

       For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.

AVAILABILITY

       The readprofile command is part of the util-linux package which can be downloaded from Linux Kernel
       Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.

util-linux 2.40.2                                  2024-04-24                                     READPROFILE(8)