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       readprofile - a tool to 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

       Available command line options are the following:

       -m mapfile
	      Specify a mapfile, which by default is /usr/src/linux/System.map.  You should spec-
	      ify 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 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 ker-
	      nel 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 fre-
	      quency, 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 func-
	      tion, 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.

       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

       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  avail-
       able,  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/System.map  The symbol table for the kernel.
       /usr/src/linux/* 	  The program being profiled :-)

4th Berkeley Distribution		     May 1996				   READPROFILE(1)
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