Kernel questions

[Brandon Hale]

On Mon, 2004-11-29 at 20:02 +0100, Nikolai Prokoschenko wrote:
> Hello!
> 
> I'm new to Ubuntu, so don't hit me too hard ;)

Wham!

> I'd like to know what the Ubuntu Linux kernel is supposed to be. I
> understand that it's derived from the Debian kernel with some patches
> merged (mostly firmware). I guess the patch merging part is why 2.6.9 is
> still not in Ubuntu while already in Debian Sid.

Reading changelog.Debian.gz provided by your linux-image will give
you a quick rundown of what has been added since Ubuntu branched the
Debian kernel.

If you are interested in seeing the actual patchset, you might grab
linux-patch-debian-2.6.8.1.

> However, what else does Ubuntu patch into the kernel, or willing to,
> considering the project goals? Myself, as an Asus S5200 notebook user
> without working ACPI out-of-the-box, would like to see the current
> acpi-branch merged with the kernel, as it is known to solve some issues,
> maybe the current -ac or -mm branch? -mm would be logical, since Ubuntu
> wants to be present on the Desktop. Are such steps planned or is it more
> likely to never happen?

Judging from the current pace of development on the Ubuntu/Debian
kernel, I can tell you that real fixes are greatly preferred to large
merges/changes.  If you can pinpoint a specific change on acpi-bk that
allows your laptop to function properly, I imagine it would be accepted
much more quickly than a full merge.

The same goes for merging bits from other trees you mention here like
-ac or -mm. While RedHat has based its own kernels on the -ac branch
during 2.4 days, it is the current Debian approach to pull in patches
that fix a specific issue or patch a security hole. AFAICT, -ac
currently does not maintain a changelog, possibly due to merging
yet-unannounced security fixes. This seems like it makes a weaker
candidate for a merge, as one would have to read all the code (its
getting to be a sizeable diff), or interdiff the current -ac patch with
earlier, better documented patches.

As for -mm, you appear to suffer from two common misconceptions that I
can hopefully clear up here.

1) Ubuntu is primarily a Desktop OS.
This is false, there is plenty of OSS server oriented software for
Ubuntu, both in main and universe. The server is not a second class
citizen in Ubuntu-land.

2) -mm is a Desktop Kernel
There seems to be a common belief that Andrew Morton's -mm pre-Linus
tree has inherently better performance than a stock kernel.org build.
This probably stems from the fact that many scheduler improvements
landing throughout the 2.6 development cycle have debuted in -mm.
Currently, pending scheduler optimizations appear to be small.

-mm is highly experimental, and solely exists to give some patches a bit
of airtime on experienced hackers systems so that he can better judge if
the patch should go back to the "drawing board", or get some small fixes
and go to Linus. There have been several occasions when I have found an
-mm release to fail even a compile or boot.  More often there are more
subtle (but nasty) issues.
-mm does *not* have magic desktop voodoo, and it is *not* a distribution
targeted kernel.
As I've mentioned a few times now, you are likely to have a higher
success rate proposing specific fixes or improvements from -mm be merged
by Ubuntu.

Hope this clears a few things up.

-- 
Brandon Hale <brandon at smarterits.com>