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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | VERSION | DESCRIPTION | OPTIONS | FILES | BUGS | EXAMPLE | REPORTING BUGS | AVAILABILITY |
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READPROFILE(8) System Administration READPROFILE(8)
readprofile - read kernel profiling information
readprofile [options]
This manpage documents version 2.0 of the program.
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.
-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(1) or
cp(1). 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.
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
/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 :-)
readprofile only works with a 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.
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 'frozen' 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
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The readprofile command is part of the util-linux package which
can be downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) If you discover any
rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to [email protected]
util-linux 2.42-start-521-ec46 2025-01-16 READPROFILE(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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