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Old 03-14-2012, 03:52 PM
Leann Ogasawara
 
Default Drop Non-smp PowerPC Kernel Flavor

Hi All,

The Ubuntu Kernel Team has been evaluating some of the current
maintenance burdens for the upcoming Precise Pangolin 12.04 LTS release.
One area which would reduce the maintenance costs would be to drop the
non-smp PowerPC kernel flavor. There are currently three PowerPC
flavors:

* non-smp (linux-image-powerpc)
* smp (linux-image-powerpc-smp)
* smp-64 (linux-image-powerpc64-smp)

Even though PowerPC is a community maintained port [1], the PowerPC
kernels are still generated along side the officially supported distro
kernels. Taking that into consideration, every PowerPC flavor takes
~2hrs to build, ie. ~6hrs for all three flavors. Given the number of
official builds and test builds that are performed over the life of the
LTS, this equates to a significant amount of time.

We would thus like to propose dropping the non-smp PowerPC kernel
flavor. Doing so would also require the installer to be updated, hence
CC'ing Colin Watson. We'd like to drop this as soon as possible, in
time for Beta-2 would be ideal.

Thoughts?

Thanks,
Leann Ogasawara

[1] https://lists.ubuntu.com/archives/ubuntu-announce/2007-February/000098.html


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Old 03-14-2012, 03:59 PM
Micah Gersten
 
Default Drop Non-smp PowerPC Kernel Flavor

On 03/14/2012 11:52 AM, Leann Ogasawara wrote:
> Hi All,
>
> The Ubuntu Kernel Team has been evaluating some of the current
> maintenance burdens for the upcoming Precise Pangolin 12.04 LTS release.
> One area which would reduce the maintenance costs would be to drop the
> non-smp PowerPC kernel flavor. There are currently three PowerPC
> flavors:
>
> * non-smp (linux-image-powerpc)
> * smp (linux-image-powerpc-smp)
> * smp-64 (linux-image-powerpc64-smp)
>
> Even though PowerPC is a community maintained port [1], the PowerPC
> kernels are still generated along side the officially supported distro
> kernels. Taking that into consideration, every PowerPC flavor takes
> ~2hrs to build, ie. ~6hrs for all three flavors. Given the number of
> official builds and test builds that are performed over the life of the
> LTS, this equates to a significant amount of time.
>
> We would thus like to propose dropping the non-smp PowerPC kernel
> flavor. Doing so would also require the installer to be updated, hence
> CC'ing Colin Watson. We'd like to drop this as soon as possible, in
> time for Beta-2 would be ideal.
>
> Thoughts?
>
> Thanks,
> Leann Ogasawara
>
> [1] https://lists.ubuntu.com/archives/ubuntu-announce/2007-February/000098.html
>
>
What's the impact on supported PowerPC hardware?

Micah

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Old 03-14-2012, 04:00 PM
Colin Watson
 
Default Drop Non-smp PowerPC Kernel Flavor

On Wed, Mar 14, 2012 at 09:52:01AM -0700, Leann Ogasawara wrote:
> The Ubuntu Kernel Team has been evaluating some of the current
> maintenance burdens for the upcoming Precise Pangolin 12.04 LTS release.
> One area which would reduce the maintenance costs would be to drop the
> non-smp PowerPC kernel flavor. There are currently three PowerPC
> flavors:

Making the associated installer changes shouldn't be a big deal, but I
suggest you ask the Xubuntu and Lubuntu communities about this since a
good proportion of powerpc users are there.

> * non-smp (linux-image-powerpc)
> * smp (linux-image-powerpc-smp)
> * smp-64 (linux-image-powerpc64-smp)

It's not clear to me whether it would make more sense to drop -powerpc
or -powerpc-smp. My memory is that -powerpc-smp was significantly less
used and would be a better candidate for removal. Do you have notes on
which hardware is covered by -powerpc-smp that can't use -powerpc64-smp?

--
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Old 03-14-2012, 04:05 PM
Micah Gersten
 
Default Drop Non-smp PowerPC Kernel Flavor

On 03/14/2012 12:00 PM, Colin Watson wrote:
> On Wed, Mar 14, 2012 at 09:52:01AM -0700, Leann Ogasawara wrote:
>> The Ubuntu Kernel Team has been evaluating some of the current
>> maintenance burdens for the upcoming Precise Pangolin 12.04 LTS release.
>> One area which would reduce the maintenance costs would be to drop the
>> non-smp PowerPC kernel flavor. There are currently three PowerPC
>> flavors:
> Making the associated installer changes shouldn't be a big deal, but I
> suggest you ask the Xubuntu and Lubuntu communities about this since a
> good proportion of powerpc users are there.
>
Xubuntu stopped producing PowerPC images due to a lack of testers. If
there's interest in these, and people committed to testing, they could
be reinstated.

Thanks,
Micah

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Old 03-14-2012, 04:23 PM
Tim Gardner
 
Default Drop Non-smp PowerPC Kernel Flavor

On 03/14/2012 11:00 AM, Colin Watson wrote:

On Wed, Mar 14, 2012 at 09:52:01AM -0700, Leann Ogasawara wrote:

The Ubuntu Kernel Team has been evaluating some of the current
maintenance burdens for the upcoming Precise Pangolin 12.04 LTS release.
One area which would reduce the maintenance costs would be to drop the
non-smp PowerPC kernel flavor. There are currently three PowerPC
flavors:


Making the associated installer changes shouldn't be a big deal, but I
suggest you ask the Xubuntu and Lubuntu communities about this since a
good proportion of powerpc users are there.


* non-smp (linux-image-powerpc)
* smp (linux-image-powerpc-smp)
* smp-64 (linux-image-powerpc64-smp)


It's not clear to me whether it would make more sense to drop -powerpc
or -powerpc-smp. My memory is that -powerpc-smp was significantly less
used and would be a better candidate for removal. Do you have notes on
which hardware is covered by -powerpc-smp that can't use -powerpc64-smp?



We consulted Jeremy Kerr about this. He says that an SMP kernel will run
on all 32 bit powerpc platforms, including non-SMP. I don't recall
discussing if the 64 bit SMP kernel would run on all SMP capable
hardware. That combination is not possible on all x86 platforms, so I
was likely biased.


rtg
--
Tim Gardner tim.gardner@canonical.com

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Old 03-14-2012, 04:39 PM
Leann Ogasawara
 
Default Drop Non-smp PowerPC Kernel Flavor

On Wed, 2012-03-14 at 11:59 -0500, Micah Gersten wrote:
> On 03/14/2012 11:52 AM, Leann Ogasawara wrote:
> > Hi All,
> >
> > The Ubuntu Kernel Team has been evaluating some of the current
> > maintenance burdens for the upcoming Precise Pangolin 12.04 LTS release.
> > One area which would reduce the maintenance costs would be to drop the
> > non-smp PowerPC kernel flavor. There are currently three PowerPC
> > flavors:
> >
> > * non-smp (linux-image-powerpc)
> > * smp (linux-image-powerpc-smp)
> > * smp-64 (linux-image-powerpc64-smp)
> >
> > Even though PowerPC is a community maintained port [1], the PowerPC
> > kernels are still generated along side the officially supported distro
> > kernels. Taking that into consideration, every PowerPC flavor takes
> > ~2hrs to build, ie. ~6hrs for all three flavors. Given the number of
> > official builds and test builds that are performed over the life of the
> > LTS, this equates to a significant amount of time.
> >
> > We would thus like to propose dropping the non-smp PowerPC kernel
> > flavor. Doing so would also require the installer to be updated, hence
> > CC'ing Colin Watson. We'd like to drop this as soon as possible, in
> > time for Beta-2 would be ideal.
> >
> > Thoughts?
> >
> > Thanks,
> > Leann Ogasawara
> >
> > [1] https://lists.ubuntu.com/archives/ubuntu-announce/2007-February/000098.html
> >
> >
> What's the impact on supported PowerPC hardware?

Jeremy Kerr did some testing a while back and noted that the PowerPC smp
flavor should run on non-smp hardware, but did acknowledge there could
be a slight performance degradation. Jeremy, do you still have the data
available?

Thanks,
Leann


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Old 03-14-2012, 05:01 PM
Leann Ogasawara
 
Default Drop Non-smp PowerPC Kernel Flavor

On Wed, 2012-03-14 at 17:00 +0000, Colin Watson wrote:
> On Wed, Mar 14, 2012 at 09:52:01AM -0700, Leann Ogasawara wrote:
> > The Ubuntu Kernel Team has been evaluating some of the current
> > maintenance burdens for the upcoming Precise Pangolin 12.04 LTS release.
> > One area which would reduce the maintenance costs would be to drop the
> > non-smp PowerPC kernel flavor. There are currently three PowerPC
> > flavors:
>
> Making the associated installer changes shouldn't be a big deal, but I
> suggest you ask the Xubuntu and Lubuntu communities about this since a
> good proportion of powerpc users are there.

Adding lubuntu-users and Julien Lavergne to the discussion to get their
feedback regarding the impact on Lubuntu users.

As Micah noted, Xubuntu stopped producing PowerPC images due to a lack
of testers.

> > * non-smp (linux-image-powerpc)
> > * smp (linux-image-powerpc-smp)
> > * smp-64 (linux-image-powerpc64-smp)
>
> It's not clear to me whether it would make more sense to drop -powerpc
> or -powerpc-smp. My memory is that -powerpc-smp was significantly less
> used and would be a better candidate for removal. Do you have notes on
> which hardware is covered by -powerpc-smp that can't use -powerpc64-smp?
>
> --
> Colin Watson [cjwatson@ubuntu.com]
>



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Old 03-14-2012, 11:51 PM
Jeremy Kerr
 
Default Drop Non-smp PowerPC Kernel Flavor

Hi Leann,


Jeremy Kerr did some testing a while back and noted that the PowerPC smp
flavor should run on non-smp hardware, but did acknowledge there could
be a slight performance degradation. Jeremy, do you still have the data
available?



I haven't done any testing myself, so don't have any quantitative data
on the performance impact. This was just information from checking out
the kernel source and having a chat with Ben H, the powerpc kernel
maintainer.


The issue is that some SMP-specific components will be present on UP
builds, mainly spinlocks. Of course, there'll be no lock contention, but
the instructions are still present. ISTR the estimate was around 1-2%
performance difference.


Cheers,


Jeremy

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Old 03-15-2012, 02:02 AM
Jeremy Kerr
 
Default Drop Non-smp PowerPC Kernel Flavor

Hi all,


We consulted Jeremy Kerr about this. He says that an SMP kernel will run
on all 32 bit powerpc platforms, including non-SMP.



To clarify: the hardware supported by the powerpc and powerpc-smp
flavours is almost identical. The differences probably don't matter
Ubuntu users, as it'll be obscure hardware. I've CC-ed benh in case he
wants to correct me on this one.


However, the SMP kernel supports (surprise!) bringing up >1 CPU on
machines that have >1 CPU. With a UP kernel on these machines, the other
CPUs are left doing nothing.


The main class of 32-bit SMP powerpc machines are the Apple dual-G4s.

So, since the hardware coverage is essentially the same, but we get SMP
support on SMP machines, I'd say that we would prefer the powerpc-smp
kernel over the powerpc flavour.


The drawback is that UP machines have a little overhead for things like
spinlocks, which are compiled-out on the UP kernel.




I don't recall
discussing if the 64 bit SMP kernel would run on all SMP capable
hardware.



No, there's 32-bit SMP hardware that will not run a 64-bit kernel.

Cheers,


Jeremy

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Old 03-15-2012, 11:02 AM
Colin Watson
 
Default Drop Non-smp PowerPC Kernel Flavor

On Thu, Mar 15, 2012 at 11:02:09AM +0800, Jeremy Kerr wrote:
> Hi all,
> >We consulted Jeremy Kerr about this. He says that an SMP kernel will run
> >on all 32 bit powerpc platforms, including non-SMP.
>
> To clarify: the hardware supported by the powerpc and powerpc-smp
> flavours is almost identical. The differences probably don't matter
> Ubuntu users, as it'll be obscure hardware. I've CC-ed benh in case
> he wants to correct me on this one.
>
> However, the SMP kernel supports (surprise!) bringing up >1 CPU on
> machines that have >1 CPU. With a UP kernel on these machines, the
> other CPUs are left doing nothing.
>
> The main class of 32-bit SMP powerpc machines are the Apple dual-G4s.
>
> So, since the hardware coverage is essentially the same, but we get
> SMP support on SMP machines, I'd say that we would prefer the
> powerpc-smp kernel over the powerpc flavour.

OK, that all makes sense, and I agree based on that. I'd forgotten
about the dual G4 class.

I would switch the installer over to powerpc-smp today, then, except
that the kernel doesn't ship powerpc-smp udebs yet, only powerpc and
powerpc64-smp. Can somebody fix that so that I can do this transition?

--
Colin Watson [cjwatson@ubuntu.com]

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