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Documentation / basic_profiling.txt

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Based on kernel version 4.0. Page generated on 2015-04-14 21:19 EST.

1	These instructions are deliberately very basic. If you want something clever,
2	go read the real docs ;-) Please don't add more stuff, but feel free to 
3	correct my mistakes ;-)    (mbligh@aracnet.com)
4	Thanks to John Levon, Dave Hansen, et al. for help writing this.
6	<test> is the thing you're trying to measure.
7	Make sure you have the correct System.map / vmlinux referenced!
9	It is probably easiest to use "make install" for linux and hack
10	/sbin/installkernel to copy vmlinux to /boot, in addition to vmlinuz,
11	config, System.map, which are usually installed by default.
13	Readprofile
14	-----------
15	A recent readprofile command is needed for 2.6, such as found in util-linux
16	2.12a, which can be downloaded from:
18	http://www.kernel.org/pub/linux/utils/util-linux/
20	Most distributions will ship it already.
22	Add "profile=2" to the kernel command line.
24	clear		readprofile -r
25			<test>
26	dump output	readprofile -m /boot/System.map > captured_profile
28	Oprofile
29	--------
31	Get the source (see Changes for required version) from
32	http://oprofile.sourceforge.net/ and add "idle=poll" to the kernel command
33	line.
35	Configure with CONFIG_PROFILING=y and CONFIG_OPROFILE=y & reboot on new kernel
37	./configure --with-kernel-support
38	make install
40	For superior results, be sure to enable the local APIC. If opreport sees
41	a 0Hz CPU, APIC was not on. Be aware that idle=poll may mean a performance
42	penalty.
44	One time setup:
45			opcontrol --setup --vmlinux=/boot/vmlinux
47	clear		opcontrol --reset
48	start		opcontrol --start
49			<test>
50	stop		opcontrol --stop
51	dump output	opreport >  output_file
53	To only report on the kernel, run opreport -l /boot/vmlinux > output_file
55	A reset is needed to clear old statistics, which survive a reboot.
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