path: root/Documentation/basic_profiling.txt
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authorLinus Torvalds <>2005-04-16 15:20:36 -0700
committerLinus Torvalds <>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/basic_profiling.txt
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+These instructions are deliberately very basic. If you want something clever,
+go read the real docs ;-) Please don't add more stuff, but feel free to
+correct my mistakes ;-) (
+Thanks to John Levon, Dave Hansen, et al. for help writing this.
+<test> is the thing you're trying to measure.
+Make sure you have the correct / vmlinux referenced!
+It is probably easiest to use "make install" for linux and hack
+/sbin/installkernel to copy vmlinux to /boot, in addition to vmlinuz,
+config,, which are usually installed by default.
+A recent readprofile command is needed for 2.6, such as found in util-linux
+2.12a, which can be downloaded from:
+Most distributions will ship it already.
+Add "profile=2" to the kernel command line.
+clear readprofile -r
+ <test>
+dump output readprofile -m /boot/ > captured_profile
+Get the source (I use 0.8) from
+and add "idle=poll" to the kernel command line
+Configure with CONFIG_PROFILING=y and CONFIG_OPROFILE=y & reboot on new kernel
+./configure --with-kernel-support
+make install
+For superior results, be sure to enable the local APIC. If opreport sees
+a 0Hz CPU, APIC was not on. Be aware that idle=poll may mean a performance
+One time setup:
+ opcontrol --setup --vmlinux=/boot/vmlinux
+clear opcontrol --reset
+start opcontrol --start
+ <test>
+stop opcontrol --stop
+dump output opreport > output_file
+To only report on the kernel, run opreport /boot/vmlinux > output_file
+A reset is needed to clear old statistics, which survive a reboot.