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NAME | SYNOPSIS | VERSION | DESCRIPTION | OPTIONS | FILES | BUGS | EXAMPLE | AVAILABILITY | COLOPHON |
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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' 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.
/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
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/⟩.
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
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2020-12-18. (At that time, the date of the most recent commit
that was found in the repository was 2020-12-17.) 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 man-pages@man7.org
util-linux October 2011 READPROFILE(8)
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