linux/Documentation/basic_profiling.txt
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   1These instructions are deliberately very basic. If you want something clever,
   2go read the real docs ;-) Please don't add more stuff, but feel free to 
   3correct my mistakes ;-)    (mbligh@aracnet.com)
   4Thanks to John Levon, Dave Hansen, et al. for help writing this.
   5
   6<test> is the thing you're trying to measure.
   7Make sure you have the correct System.map / vmlinux referenced!
   8
   9It is probably easiest to use "make install" for linux and hack
  10/sbin/installkernel to copy vmlinux to /boot, in addition to vmlinuz,
  11config, System.map, which are usually installed by default.
  12
  13Readprofile
  14-----------
  15A recent readprofile command is needed for 2.6, such as found in util-linux
  162.12a, which can be downloaded from:
  17
  18http://www.kernel.org/pub/linux/utils/util-linux/
  19
  20Most distributions will ship it already.
  21
  22Add "profile=2" to the kernel command line.
  23
  24clear           readprofile -r
  25                <test>
  26dump output     readprofile -m /boot/System.map > captured_profile
  27
  28Oprofile
  29--------
  30
  31Get the source (see Changes for required version) from
  32http://oprofile.sourceforge.net/ and add "idle=poll" to the kernel command
  33line.
  34
  35Configure with CONFIG_PROFILING=y and CONFIG_OPROFILE=y & reboot on new kernel
  36
  37./configure --with-kernel-support
  38make install
  39
  40For superior results, be sure to enable the local APIC. If opreport sees
  41a 0Hz CPU, APIC was not on. Be aware that idle=poll may mean a performance
  42penalty.
  43
  44One time setup:
  45                opcontrol --setup --vmlinux=/boot/vmlinux
  46
  47clear           opcontrol --reset
  48start           opcontrol --start
  49                <test>
  50stop            opcontrol --stop
  51dump output     opreport >  output_file
  52
  53To only report on the kernel, run opreport -l /boot/vmlinux > output_file
  54
  55A reset is needed to clear old statistics, which survive a reboot.
  56
  57
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