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]
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VERSION

12       This manpage documents version 2.0 of the program.
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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.
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OPTIONS

24       -a, --all
25              Print  all  symbols  in  the mapfile.  By default the procedures
26              with reported ticks are not printed.
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28       -b, --histbin
29              Print individual histogram-bin counts.
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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.
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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.
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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.  This is supported  on  i386-SMP
51              (2.2  and 2.4 kernel) and also on sparc-SMP and sparc64-SMP (2.4
52              kernel).  This option also  resets  the  profiling  buffer,  and
53              requires superuser privileges.
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55       -p, --profile pro-file
56              Specify  a  different  profiling  buffer,  which  by  default is
57              /proc/profile.  Using a different pro-file is useful if you want
58              to `freeze' the kernel profiling at some time and read it later.
59              The /proc/profile file can be copied using `cat' or `cp'.  There
60              is no more support for compressed profile buffers, like in read‐
61              profile-1.1, because the program needs to know the size  of  the
62              buffer in advance.
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64       -r, --reset
65              Reset  the  profiling buffer.  This can only be invoked by root,
66              because /proc/profile is readable by everybody but writable only
67              by  the  superuser.  However, you can make readprofile setuid 0,
68              in order to reset the buffer without gaining privileges.
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70       -s, --counters
71              Print individual counters within functions.
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73       -v, --verbose
74              Verbose.  The output is organized in  four  columns  and  filled
75              with  blanks.   The  first column is the RAM address of a kernel
76              function, the second is the name of the function, the  third  is
77              the number of clock ticks and the last is the normalized load.
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79       -V, --version
80              This makes readprofile print its version number and exit.
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82       -h, --help
83              Display help and exit.
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EXAMPLES

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

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

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

127       The readprofile command is part of the util-linux package and is avail‐
128       able from Linux  Kernel  Archive  ⟨ftp://ftp.kernel.org/pub/linux/utils
129       /util-linux/⟩.
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133util-linux                       October 2011                   READPROFILE(8)
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