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. ```` 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 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 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.