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READPROFILE(8) System Administration READPROFILE(8)
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(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.
-V, --version
Display version information and exit.
-h, --help
Display help text and exit.
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 :-)
BUGS
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.
EXAMPLE
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
REPORTING BUGS
For bug reports, use the issue tracker at https://github.com/karelzak/util-linux/issues.
AVAILABILITY
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/>.
util-linux 2.37.2 2021-06-02 READPROFILE(8)
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