readprofile - read kernel profiling information
This manpage documents version 2.0 of the program.
command uses the /proc/profile
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
- -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
- -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. 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/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
- -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.
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
only works with an 1.3.x or newer kernel, because
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
/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 :-)
The readprofile command is part of the util-linux package and is available from