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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