1READPROFILE(8)               System Administration              READPROFILE(8)
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NAME

6       readprofile - read kernel profiling information
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SYNOPSIS

9       readprofile [options]
10

VERSION

12       This manpage documents version 2.0 of the program.
13

DESCRIPTION

15       The readprofile command uses the /proc/profile information to print
16       ascii data on standard output. The output is organized in three
17       columns: the first is the number of clock ticks, the second is the name
18       of the C function in the kernel where those many ticks occurred, and
19       the third is the normalized `load' of the procedure, calculated as a
20       ratio between the number of ticks and the length of the procedure. The
21       output is filled with blanks to ease readability.
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OPTIONS

24       -a, --all
25           Print all symbols in the mapfile. By default the procedures with
26           reported ticks are not printed.
27
28       -b, --histbin
29           Print individual histogram-bin counts.
30
31       -i, --info
32           Info. This makes readprofile only print the profiling step used by
33           the kernel. The profiling step is the resolution of the profiling
34           buffer, and is chosen during kernel configuration (through make
35           config), or in the kernel’s command line. If the -t (terse) switch
36           is used together with -i only the decimal number is printed.
37
38       -m, --mapfile mapfile
39           Specify a mapfile, which by default is /usr/src/linux/System.map.
40           You should specify the map file on cmdline if your current kernel
41           isn’t the last one you compiled, or if you keep System.map
42           elsewhere. If the name of the map file ends with .gz it is
43           decompressed on the fly.
44
45       -M, --multiplier multiplier
46           On some architectures it is possible to alter the frequency at
47           which the kernel delivers profiling interrupts to each CPU. This
48           option allows you to set the frequency, as a multiplier of the
49           system clock frequency, HZ. Linux 2.6.16 dropped multiplier support
50           for most systems. This option also resets the profiling buffer, and
51           requires superuser privileges.
52
53       -p, --profile pro-file
54           Specify a different profiling buffer, which by default is
55           /proc/profile. Using a different pro-file is useful if you want to
56           `freeze' the kernel profiling at some time and read it later. The
57           /proc/profile file can be copied using cat(1) or cp(1). There is no
58           more support for compressed profile buffers, like in
59           readprofile-1.1, because the program needs to know the size of the
60           buffer in advance.
61
62       -r, --reset
63           Reset the profiling buffer. This can only be invoked by root,
64           because /proc/profile is readable by everybody but writable only by
65           the superuser. However, you can make readprofile set-user-ID 0, in
66           order to reset the buffer without gaining privileges.
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68       -s, --counters
69           Print individual counters within functions.
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71       -v, --verbose
72           Verbose. The output is organized in four columns and filled with
73           blanks. The first column is the RAM address of a kernel function,
74           the second is the name of the function, the third is the number of
75           clock ticks and the last is the normalized load.
76
77       -h, --help
78           Display help text and exit.
79
80       -V, --version
81           Print version and exit.
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FILES

84       /proc/profile
85           A binary snapshot of the profiling buffer.
86
87       /usr/src/linux/System.map
88           The symbol table for the kernel.
89
90       /usr/src/linux/*
91           The program being profiled :-)
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BUGS

94       readprofile only works with a 1.3.x or newer kernel, because
95       /proc/profile changed in the step from 1.2 to 1.3.
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97       This program only works with ELF kernels. The change for a.out kernels
98       is trivial, and left as an exercise to the a.out user.
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100       To enable profiling, the kernel must be rebooted, because no profiling
101       module is available, and it wouldn’t be easy to build. To enable
102       profiling, you can specify profile=2 (or another number) on the kernel
103       commandline. The number you specify is the two-exponent used as
104       profiling step.
105
106       Profiling is disabled when interrupts are inhibited. This means that
107       many profiling ticks happen when interrupts are re-enabled. Watch out
108       for misleading information.
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EXAMPLE

111       Browse the profiling buffer ordering by clock ticks:
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113              readprofile | sort -nr | less
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115       Print the 20 most loaded procedures:
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117              readprofile | sort -nr +2 | head -20
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119       Print only filesystem profile:
120
121              readprofile | grep _ext2
122
123       Look at all the kernel information, with ram addresses:
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125              readprofile -av | less
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127       Browse a 'frozen' profile buffer for a non current kernel:
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129              readprofile -p ~/profile.freeze -m /zImage.map.gz
130
131       Request profiling at 2kHz per CPU, and reset the profiling buffer:
132
133              sudo readprofile -M 20
134

REPORTING BUGS

136       For bug reports, use the issue tracker at
137       https://github.com/util-linux/util-linux/issues.
138

AVAILABILITY

140       The readprofile command is part of the util-linux package which can be
141       downloaded from Linux Kernel Archive
142       <https://www.kernel.org/pub/linux/utils/util-linux/>.
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146util-linux 2.38                   2022-02-17                    READPROFILE(8)
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