1READPROFILE(8)               System Administration              READPROFILE(8)
2
3
4

NAME

6       readprofile - read kernel profiling information
7

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  col‐
17       umns: the first is the number of clock ticks, the second is the name of
18       the C function in the kernel where those many ticks occurred,  and  the
19       third  is the normalized `load' of the procedure, calculated as a ratio
20       between the number of ticks and the length of the procedure.  The  out‐
21       put is filled with blanks to ease readability.
22

OPTIONS

24       -a, --all
25              Print  all  symbols  in  the mapfile.  By default the procedures
26              with 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
33              by the kernel.  The profiling step is the resolution of the pro‐
34              filing  buffer,  and  is  chosen  during  kernel   configuration
35              (through  `make  config'),  or in the kernel's command line.  If
36              the -t (terse) switch is used together with -i only the  decimal
37              number is printed.
38
39       -m, --mapfile mapfile
40              Specify  a  mapfile,  which  by  default  is /usr/src/linux/Sys‐
41              tem.map.  You should specify the map file  on  cmdline  if  your
42              current  kernel  isn't the last one you compiled, or if you keep
43              System.map elsewhere.  If the name of the  map  file  ends  with
44              `.gz' it is decompressed on the fly.
45
46       -M, --multiplier multiplier
47              On  some  architectures it is possible to alter the frequency at
48              which the kernel delivers  profiling  interrupts  to  each  CPU.
49              This  option allows you to set the frequency, as a multiplier of
50              the system clock frequency, HZ. Linux 2.6.16 dropped  multiplier
51              support for most systems.  This option also resets the profiling
52              buffer, and requires superuser privileges.
53
54       -p, --profile pro-file
55              Specify a  different  profiling  buffer,  which  by  default  is
56              /proc/profile.  Using a different pro-file is useful if you want
57              to `freeze' the kernel profiling at some time and read it later.
58              The /proc/profile file can be copied using `cat' or `cp'.  There
59              is no more support for compressed profile buffers, like in read‐
60              profile-1.1,  because  the program needs to know the size of the
61              buffer in advance.
62
63       -r, --reset
64              Reset the profiling buffer.  This can only be invoked  by  root,
65              because /proc/profile is readable by everybody but writable only
66              by the superuser.  However, you can make readprofile set-user-ID
67              0, in order to reset the buffer without gaining privileges.
68
69       -s, --counters
70              Print individual counters within functions.
71
72       -v, --verbose
73              Verbose.   The  output  is  organized in four columns and filled
74              with blanks.  The first column is the RAM address  of  a  kernel
75              function,  the  second is the name of the function, the third is
76              the number of clock ticks and the last is the normalized load.
77
78       -V, --version
79              Display version information and exit.
80
81       -h, --help
82              Display help text and exit.
83

EXAMPLES

85       Browse the profiling buffer ordering by clock ticks:
86          readprofile | sort -nr | less
87
88       Print the 20 most loaded procedures:
89          readprofile | sort -nr +2 | head -20
90
91       Print only filesystem profile:
92          readprofile | grep _ext2
93
94       Look at all the kernel information, with ram addresses:
95          readprofile -av | less
96
97       Browse a `freezed' profile buffer for a non current kernel:
98          readprofile -p ~/profile.freeze -m /zImage.map.gz
99
100       Request profiling at 2kHz per CPU, and reset the profiling buffer:
101          sudo readprofile -M 20
102

BUGS

104       readprofile  only  works  with  an  1.3.x  or  newer  kernel,   because
105       /proc/profile changed in the step from 1.2 to 1.3
106
107       This program only works with ELF kernels.  The change for a.out kernels
108       is trivial, and left as an exercise to the a.out user.
109
110       To enable profiling, the kernel must be rebooted, because no  profiling
111       module  is available, and it wouldn't be easy to build.  To enable pro‐
112       filing, you can specify "profile=2" (or another number) on  the  kernel
113       commandline.   The  number you specify is the two-exponent used as pro‐
114       filing step.
115
116       Profiling is disabled when interrupts are inhibited.  This  means  that
117       many  profiling ticks happen when interrupts are re-enabled.  Watch out
118       for misleading information.
119

FILES

121       /proc/profile              A binary snapshot of the profiling buffer.
122       /usr/src/linux/System.map  The symbol table for the kernel.
123       /usr/src/linux/*           The program being profiled :-)
124

AVAILABILITY

126       The readprofile command is part of the util-linux package and is avail‐
127       able  from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils
128       /util-linux/⟩.
129
130
131
132util-linux                       October 2011                   READPROFILE(8)
Impressum