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 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/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 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 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.

       -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 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 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
       ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

4th Berkeley Distribution                           May 1996                                      READPROFILE(1)