Revision a247c3a97a0216b18a46243eda26081f1928ec37 authored by Andrea Arcangeli on 22 September 2010, 20:05:12 UTC, committed by Linus Torvalds on 23 September 2010, 00:22:39 UTC
The below bug in fork led to the rmap walk finding the parent huge-pmd twice instead of just once, because the anon_vma_chain objects of the child vma still point to the vma->vm_mm of the parent. The patch fixes it by making the rmap walk accurate during fork. It's not a big deal normally but it worth being accurate considering the cost is the same. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Acked-by: Johannes Weiner <jweiner@redhat.com> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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basic_profiling.txt
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.
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
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.
Computing file changes ...
