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NAME    [Toc]    [Back]

       readprofile - a tool to read kernel profiling information

SYNOPSIS    [Toc]    [Back]

       readprofile [ options ]

VERSION    [Toc]    [Back]

       This manpage documents version 2.0 of the program.

DESCRIPTION    [Toc]    [Back]

       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/Sys-
	      tem.map.	You should specify the map file  on  cmdline  if  your
	      current  kernel  isn't the last one you compiled. 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 read-
	      profile-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.

       -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

EXAMPLES    [Toc]    [Back]

       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    [Toc]    [Back]

       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

       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    [Toc]    [Back]

       /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 :-)

4th Berkeley Distribution	   May 1996			READPROFILE(1)
[ Back ]
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