READPROFILE(1)

NAME
readprofile - a tool to read kernel profiling information

SYNOPSIS
readprofile [ options ]

VERSION
This manpage documents version 1.1 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 thicks and the lenght 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. To ease use of readprofile with kernels in the 1.1.7x series, if the default file can't be opened, the alternate file /usr/src/linux/zSystem.map is tried. You should specify the map file on cmdline if your current kernel isn't the last one you compiled. 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'. If the name of the pro-file ends by `.gz' it is decompressed on the fly. The pro-file is such that gzip shrinks it by 50-100 times.

-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'). 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.

-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.

-t  Terse. This causes the output to be unfilled. It is the format used in the first release of readprofile.

-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 gzipped `freezed' profile buffer for a non current kernel:
   readprofile -p ~/profile.freeze.gz -m /zImage.map

BUGS

readprofile needs a kernel version 1.1.73 or newer, because /proc/profile is absent in older versions.

To enable profiling, the kernel must be reconfigured, recompiled, and rebooted. No profiling module is available, and it wouldn't be easy to build. So this can be construed as a feature.

Profiling is disabled when interrupts are inhibited. This means that many profiling ticks happen when interrupts are re-enabled. Watch out for misleading information.

AUTHOR
Readprofile and /proc/profile are by Alessandro Rubini (rubini@ipvvis.unipv.it)

FILES
/proc/profile              A binary snapshot of the profiling buffer.
/usr/src/linux/System.map  The symbol table for the kernel.
/usr/src/linux/zSystem.map Old name for the symbol table.
/usr/src/linux/*           The program being profiled :-)