readprofile - read kernel profiling information


   readprofile [options]


   This manpage documents version 2.0 of the program.


   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.


   -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/  You should specify the map  file  on
          cmdline  if your current kernel isn't the last one you compiled,
          or if you keep 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.  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.

   -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 setuid 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.


   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 /

   Request profiling at 2kHz per CPU, and reset the profiling buffer:
      sudo readprofile -M 20


   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.


   /proc/profile              A binary snapshot of the profiling buffer.
   /usr/src/linux/  The symbol table for the kernel.
   /usr/src/linux/*           The program being profiled :-)


   The  readprofile  command  is  part  of  the  util-linux package and is
   available from  Linux  Kernel  Archive

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