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 orga-
       nized 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 resolu-
              tion of the profiling buffer, and is chosen during kernel configuration (through `make config'), or  in  the  ker-
              nel'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-ng   package   and   is   available   from   ftp://ftp.ker-
       nel.org/pub/linux/utils/util-linux-ng/.



4th Berkeley Distribution                                   May 1996                                              READPROFILE(1)