Re: Wheezy NSS...
Hi,
On Tue, Oct 23, 2012 at 08:45:25PM -0700, Jonathan Nieder wrote:
> Dave Jones wrote:
> > Can the wheezy s390x kernel be saved as an NSS? If so, how?
> Based on [1], it looks like the answer is currently no, based on the
> following line in the kernel config file:
>
> # CONFIG_SHARED_KERNEL is not set
>
> The description of that option says
>
> Select this option, if you want to share the text segment of the
> Linux kernel between different VM guests. This reduces memory
> usage with lots of guests but greatly increases kernel size.
>
> You can build a custom kernel using that option if you wish. It works
> like this[2]:
>
> $ apt-get source linux
> # apt-get install build-essential fakeroot
> # apt-get build-dep linux
> $ cd linux-<version>
> $ fakeroot debian/rules source
> $ fakeroot make -f debian/rules.gen setup_s390_none_s390x
as we're talking about s390x here that would be setup_s390x_none_s390x.
> $ cd debian/build/build_s390_none_s390x
Same here.
> $ scripts/config --disable DEBUG_INFO
> $ scripts/config --enable SHARED_KERNEL
That's «../source_none/scripts/config».
> $ cd ../../..
> $ fakeroot make -f debian/rules.gen binary-arch_s390_none_s390x
And again s390x_none_s390x instead of s390_none_s390x.
I just did the recompilation. AFAICS the kernel size is indeed increased quite
a bit. We currently have:
-rw-r--r-- root/root 6303232 2012-10-22 15:36 ./boot/vmlinuz-3.2.0-4-s390x
With SHARED_KERNEL on and DEBUG_INFO off as above:
-rw-r--r-- root/root 7945728 2012-10-25 21:53 ./boot/vmlinuz-3.2.0-4-s390x
So a NSS shareable kernel is 1.26 times larger than a plain one. And I fear
that the additional bits cannot be discarded at runtime neither, but I cannot
test this right now.
Interestingly enough the kernel is already in its plain form 2.23 times bigger
than an amd64 build of vmlinuz-3.2.0-3-amd64.
Kind regards
Philipp Kern
> [1] http://www.vm.ibm.com/linux/linuxnss.html
> [2] http://kernel-handbook.alioth.debian.org/ch-common-tasks.html
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