readprofile(8) — Linux manual page

NAME | SYNOPSIS | VERSION | DESCRIPTION | OPTIONS | FILES | BUGS | EXAMPLE | REPORTING BUGS | AVAILABILITY

READPROFILE(8)            System Administration           READPROFILE(8)

NAME         top

       readprofile - read kernel profiling information

SYNOPSIS         top

       readprofile [options]

VERSION         top

       This manpage documents version 2.0 of the program.

DESCRIPTION         top

       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         top

       -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         top

       /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         top

       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         top

       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         top

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

AVAILABILITY         top

       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/>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
       a bug report for this manual page, send it to
       util-linux@vger.kernel.org. This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2021-08-27. (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-24.) If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in
       this COLOPHON (which is not part of the original manual page),
       send a mail to man-pages@man7.org

util-linux 2.37.85-637cc       2021-04-02                 READPROFILE(8)