readprofile

READPROFILE(1)                    User Commands                   READPROFILE(1)



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)