readprofile



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, 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/Sys-
              tem.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 read-
              profile-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 pro-
              filing   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 func-
              tion, 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 pro-
       filing, you can specify "profile=2" (or another number) on  the  kernel
       commandline.   The  number you specify is the two-exponent used as pro-
       filing 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 :-)




4th Berkeley Distribution          May 1996                     READPROFILE(1)

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