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/>.