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  col-
       umns: 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  out-
       put 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 pro-
              filing  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/Sys-
              tem.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 read-
              profile-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
       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

BUGS
       readprofile only works with a 1.3.x or newer kernel, because /proc/pro-
       file 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 pro-
       filing, you can specify "profile=2" (or another number) on  the  kernel
       commandline.   The  number you specify is the two-exponent used as pro-
       filing 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
       /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
       The readprofile command is part of the util-linux package and is avail-
       able  from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils
       /util-linux/>.

util-linux                       October 2011                   READPROFILE(8)