readprofile(8) - man - phpMan

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)