69 lines
1.8 KiB
ReStructuredText
69 lines
1.8 KiB
ReStructuredText
Basic kernel profiling
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======================
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These instructions are deliberately very basic. If you want something clever,
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go read the real docs ;-)
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Please don't add more stuff, but feel free to
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correct my mistakes ;-) (mbligh@aracnet.com)
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Thanks to John Levon, Dave Hansen, et al. for help writing this.
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``<test>`` is the thing you're trying to measure.
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Make sure you have the correct ``System.map`` / ``vmlinux`` referenced!
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It is probably easiest to use ``make install`` for linux and hack
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``/sbin/installkernel`` to copy ``vmlinux`` to ``/boot``, in addition to
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``vmlinuz``, ``config``, ``System.map``, which are usually installed by default.
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Readprofile
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-----------
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A recent ``readprofile`` command is needed for 2.6, such as found in util-linux
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2.12a, which can be downloaded from:
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http://www.kernel.org/pub/linux/utils/util-linux/
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Most distributions will ship it already.
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Add ``profile=2`` to the kernel command line.
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Some ``readprofile`` commands::
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clear readprofile -r
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<test>
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dump output readprofile -m /boot/System.map > captured_profile
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Oprofile
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--------
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Get the source (see Changes for required version) from
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http://oprofile.sourceforge.net/ and add ``idle=poll`` to the kernel command
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line.
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Configure with ``CONFIG_PROFILING=y`` and ``CONFIG_OPROFILE=y`` & reboot on new kernel::
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./configure --with-kernel-support
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make install
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For superior results, be sure to enable the local APIC. If opreport sees
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a 0Hz CPU, APIC was not on. Be aware that idle=poll may mean a performance
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penalty.
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One time setup::
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opcontrol --setup --vmlinux=/boot/vmlinux
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Some ``opcontrol`` commands::
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clear opcontrol --reset
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start opcontrol --start
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<test>
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stop opcontrol --stop
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dump output opreport > output_file
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To only report on the kernel, run ``opreport -l /boot/vmlinux > output_file``
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A reset is needed to clear old statistics, which survive a reboot.
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