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READPROFILE(1)                                                  READPROFILE(1)



NAME
       readprofile - a tool to 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, calcu-
       lated 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 con-
              fig'), or in the kernel's command line.  If the -t (terse) switch is used together with -i only the dec-
              imal 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  privi-
              leges.


       -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 inter-
       rupts 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-ng  package  and  is  available  from   ftp://ftp.ker-
       nel.org/pub/linux/utils/util-linux-ng/.



4th Berkeley Distribution          May 1996                     READPROFILE(1)