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diff --git a/Documentation/admin-guide/basic-profiling.rst b/Documentation/admin-guide/basic-profiling.rst new file mode 100644 index 000000000000..72babc71b771 --- /dev/null +++ b/Documentation/admin-guide/basic-profiling.rst @@ -0,0 +1,68 @@ +Basic kernel profiling +====================== + + +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 ;-) (mbligh@aracnet.com) + +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 ``System.map`` / ``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``, ``System.map``, which are usually installed by default. + +Readprofile +----------- + +A recent ``readprofile`` command is needed for 2.6, such as found in util-linux +2.12a, which can be downloaded from: + + http://www.kernel.org/pub/linux/utils/util-linux/ + +Most distributions will ship it already. + +Add ``profile=2`` to the kernel command line. + +Some ``readprofile`` commands:: + + clear readprofile -r + <test> + dump output readprofile -m /boot/System.map > captured_profile + +Oprofile +-------- + +Get the source (see Changes for required version) from +http://oprofile.sourceforge.net/ 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 +penalty. + +One time setup:: + + opcontrol --setup --vmlinux=/boot/vmlinux + +Some ``opcontrol`` commands:: + + clear opcontrol --reset + start opcontrol --start + <test> + stop opcontrol --stop + dump output opreport > output_file + +To only report on the kernel, run ``opreport -l /boot/vmlinux > output_file`` + +A reset is needed to clear old statistics, which survive a reboot. |