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READPROFILE(8)                        System Administration                        READPROFILE(8)

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.

OPTIONS
       -a, --all
              Print all symbols in the mapfile.  By default the procedures  with  reported  ticks
              are not printed.

       -b, --histbin
              Print individual histogram-bin counts.

       -i, --info
              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.

       -m, --mapfile mapfile
              Specify a mapfile, which by default is /usr/src/linux/System.map.  You should spec‐
              ify 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.

       -M, --multiplier 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  fre‐
              quency,  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.

       -p, --profile 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.

       -r, --reset
              Reset  the  profiling buffer.  This can only be invoked by root, because /proc/pro‐
              file 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.

       -s, --counters
              Print individual counters within functions.

       -v, --verbose
              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
              Display version information and exit.

       -h, --help
              Display help text 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  avail‐
       able,  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  Linux
       Kernel Archive ⟨ftp://ftp.kernel.org/pub/linux/utils/util-linux/⟩.

util-linux                                 October 2011                            READPROFILE(8)

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