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 output 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 profil-
	      ing  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/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 decom-
	      pressed 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  supe-
	      ruser 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
	      This makes readprofile print its version number and exit.

       -h, --help
	      Display help 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 Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils
       /util-linux/>.

util-linux							   October 2011 						    READPROFILE(8)