readprofile

READPROFILE(8)               System Administration              READPROFILE(8)

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.

       -V, --version
           Display version information and exit.

       -h, --help
           Display help text 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/karelzak/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 2.37.2                 2021-06-02                    READPROFILE(8)