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
              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.

       -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
              frequency,  as a multiplier of the system clock frequency, HZ. Linux 2.6.16 dropped
              multiplier support for most systems.  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/profile is  readable  by  everybody  but  writable  only  by  the  superuser.
              However,  you  can  make  readprofile  set-user-ID  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
       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 Linux
       Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.