[RFC] Moving Intrepid to 2.6.27 kernel

Chuck Short zulcss at gmail.com
Mon Aug 25 19:01:25 BST 2008

+1 from me.

2.6.27 has a bunch of features that we want for virtualization that we
want for better Xen support. This includes domU support for am64
architectures and save/restore support for Xen guests. If we did not
have 2.6.27 in intrepid we would be maintaining a custom flavor that
we dont have to do now.


On Sun, Aug 24, 2008 at 10:51 PM, Ben Collins <ben.collins at canonical.com> wrote:
> Matt Zimmerman wrote:
>> On Wed, Aug 20, 2008 at 04:02:47PM -0400, Ben Collins wrote:
>>> As many of you know, we've continued a tree called ubuntu-next which is
>>> currently following 2.6.27 upstream kernel. It has been kept in sync
>>> with intrepid's 2.6.26 based kernel tree.
>> I have been in all-day meetings this past week and did not see this thread
>> until now.  I think this change requires stronger justification than I've
>> seen so far.
>>> In recent weeks it has become apparent that we will need several updates
>>> to 2.6.26 in order to have a stable kernel for 8.10. These include:
>>>  * Updated mac80211, which will require updated wlan drivers in order
>>>    to fix major regressions with suspend/resume and wlan devices.
>>>  * Updated alsa-1.0.17 drivers for new codecs
>>>  * xen64 paravirt
>>>  * Updated KVM
>>> These are just the major things we need to do.
>> Why are these needed in order to have a stable kernel for 8.10?  Major
>> updates are the opposite of stability.  What we want is a kernel which fixes
>> more bugs than it introduces while introducing the most important driver
>> updates we need for the release.
>>> The good thing is, all of this is already in 2.6.27, and is ready to be
>>> uploaded on a moments notice. It has been tested by myself for quite some
>>> time, and others on the team have also tested it.
>> The amount of testing it has received is trivial compared to what 2.6.26 has
>> seen.  It's been tested on our certified systems and by many thousands of
>> community members on their own hardware.  The fact that it's been smoke
>> tested by a few people doesn't give me much confidence that it's free of
>> serious regressions.
>>> Yesterday, we discussed the possibility of moving to 2.6.27 before
>>> feature freeze on #ubuntu-kernel during out weekly IRC meeting. In
>>> attendance were the kernel team, Steve Langasek, Chuck Short and Soren
>>> Hansen. Soren and Chuck gave particularly good reasons for moving to
>>> 2.6.27, which included xen64 and updated KVM.
>> Where can I find the summary and log of the meeting?
> I can put one together.
>>> Steve had questions about the particulars of this move, and I believe we
>>> answered all of his questions satisfyingly, but we agreed to take this
>>> to a wider audience before making a commitment.
>>> So fire away with any concerns or issues that this might cause. If we
>>> are going to do it, it needs to be decided by early next week.
>> I was in meetings all week and didn't see this until now.  Mario has raised
>> a concern in this thread which I think needs to be addressed.  I also have
>> the following questions:
> I've tested LRM, and it compiles fine. I've tested at least broadcom's
> driver.
>> What are the known regressions from 2.6.26 to 2.6.27?
> I've looked at the list of known regressions from upstream, and the
> critical/important ones have been addressed or don't affect us.
>> Which systems has 2.6.27 been tested on?  What test plan was followed?
> I've tested 32-bit and 64-bit on Xeon, 4+ laptops and a few of Intel's
> SDP's. Tim has done further testing. I know the server team has been
> checking the 2.6.27 kernels as well. In addition, I've had feedback from
> more than a dozen others that have been using the 2.6.27 kernels on
> various platforms because of fixes major problems for them over 2.6.26.
>> In which areas are further regressions to be expected in 2.6.27 (which parts
>> of the kernel have changed in the most significant ways)?
> Alsa and wireless are the major areas. In 2.6.26 there were major
> updates to RTC, which seem to have settled now in 2.6.27. Alsa and
> wireless are major improvements over 2.6.26.
> The problem with 2.6.26 is that wireless updates there are causing major
> regressions in suspend/resume, which as far as I'm concerned is a
> showstopper in itself. 2.6.27 fixes these issues.
> Also included in the wireless update is ath5k/ath9k updates, which could
> make madwifi unneeded, stomping out one lrm driver. There's also a new
> iwlagn driver and iwl5k driver, bringing better support for newer Intel
> wireless cards, including 11n support for 4965 (these new drivers
> require the new wireless stack, so we can't just grab the drivers).
> Updating to Alsa 1.0.17 is a must-have for intrepid due to various
> driver updates. If we release with 1.0.16 (which is in 2.6.26) we wont
> be supporting a lot of new hardware.
>> What were the results of certification testing with 2.6.27?
> No results that I know of. We have no way to do one-off certification
> testing that I'm aware of.
> We aren't getting rid of the 2.6.26 tree, so worse case, we revert back
> to it. But I have strong indications right now that we wont need to
> consider that.
> Our main reason to do this is that 2.6.26 as-is isn't good enough to
> release intrepid. Updating the various stacks to improve the state will
> require more effort on our part than updating the whole kernel
> (especially in the long term for security and such).
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