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.

       Available command line options are the following:

       -m 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.

       -p 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.

       -i     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.

       -a     Print all symbols in the mapfile. By default the procedures with 0  reported  ticks
              are not printed.

       -b     Print individual histogram-bin counts.

       -r     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 setuid 0, in order to reset the buffer without gaining privileges.

       -M 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.  This is supported on
              i386-SMP (2.2 and 2.4 kernel) and also on sparc-SMP and sparc64-SMP  (2.4  kernel).
              This option also resets the profiling buffer, and requires superuser privileges.

       -v     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. This makes readprofile print its version number 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 `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

       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

       /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
       ftp://ftp.kernel.org/pub/linux/utils/util-linux/.