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' 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

       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/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

       /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 available from Linux Kernel Archive.

util-linux                                        October 2011                                    READPROFILE(8)