NAME | SYNOPSIS | VERSION | DESCRIPTION | OPTIONS | EXAMPLES | BUGS | FILES | AVAILABILITY | COLOPHON

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' or
              `cp'.  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.

EXAMPLES         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 `freezed' 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

BUGS         top

       readprofile only works with an 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.

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 :-)

AVAILABILITY         top

       The readprofile command is part of the util-linux package and is
       available from Linux Kernel Archive 
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.

COLOPHON         top

       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
       2017-09-15.  If you discover any rendering problems in this HTML ver‐
       sion 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 man‐
       ual page), send a mail to man-pages@man7.org

util-linux                      October 2011                  READPROFILE(8)