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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.  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 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 `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  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)
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