Bug#620297: base: vmstat and /proc/loadavg disagree

[Jonathan Nieder <jrnieder@gmail.com>]

found 620297 linux-2.6/2.6.32-30
found 620297 linux-2.6/2.6.32-36
tags 620297 + patch moreinfo
quit

Hi,

Aman Gupta wrote:

> The Ubuntu guys pulled the two upstream patches into their 2.6.32
> build, and the RedHat guys did the same in their 2.6.35 and 2.6.38
> builds. Is there anything preventing us from pulling in the patches
> too?

I'm coming in late; please forgive my ignorance.

I assume the two patches in question are

 v2.6.35-rc1~521^2~16 (sched: Cure load average vs NO_HZ woes, 2010-08-22)
 v2.6.37-rc7~13^2~5 (sched: Cure more NO_HZ load average woes, 2010-11-30)

The first does not apply cleanly to the 2.6.32.y tree but Lesław Kopeć
backported it.  The other applies cleanly on top (and can be retrieved
in patch form with "git show v2.6.37-rc7~13^2~5").

So what would be most useful is:

 1. Try a pristine 2.6.32.y kernel, to make sure it reproduces the problem.
    If you already have a git checkout of the kernel:

	cd linux
	git remote add stable \
	  git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
	git fetch stable

    Otherwise:

	git clone -o stable \
	  git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git \
	  linux
	cd linux

    Then build and test:

	git checkout stable/linux-2.6.32.y
	cp /boot/config-$(uname -r) .config; # stock configuration
	make localmodconfig; # optional: minimize configuration
	make deb-pkg; # optionally with -j<n> for parallel build
	dpkg -i ../<name of package>
	reboot

 2. Try the patches, to make sure they fix it.

	cd linux
	git apply --index patch1
	git apply --index patch2
	make deb-pkg; # maybe with -j4
	dpkg -i ../<name of package>
	reboot

If the problem is reproducible with current 2.6.32.y and the patches fix it,
we can submit them upstream so everyone benefits.

Thanks and hope that helps,
Jonathan