Modular Kernel Packaging for Cloud

[Sandro "red" Mathys]

On Fri, Mar 7, 2014 at 3:10 AM, Josh Boyer <jwboyer at fedoraproject.org> wrote:
> On Thu, Mar 6, 2014 at 12:04 PM, Don Zickus <dzickus at redhat.com> wrote:
>> On Thu, Mar 06, 2014 at 11:32:55AM -0500, Matthew Miller wrote:
>>> On Thu, Mar 06, 2014 at 11:02:47AM -0500, Josh Boyer wrote:
>>> > If it's _necessary_, that's one thing.  I've yet to really see any data
>>> > backing up necessity on any of this at all though.  Right now it seems
>>> > to be sitting in the "nice to have" category.
>>>
>>> For the record, it is _literally_ sitting in our "nice to have" category.
>>> See
>>> https://fedoraproject.org/wiki/Cloud_Changelist#Change:_Cloud-Friendly_Kernel_Packaging
>>>
>>> :)
>>>
>>>
>>> > Perhaps someone from the cloud team could look at existing images from
>>> > other distros and figure out kernel sizes there, and how it plays into
>>> > usage and cost in those environments?
>>>
>>> On the ubuntu EC2 image, /lib/modules/$(uname -r) is 24M + 5.2M vmlinuz +
>>> 1.1M in /lib/firmware. Total package size is 32M on disk. And 5.9M initrd.
>>>
>>> CoreOS is bigger, with 33M in /lib/modules and 5.2M in lib/firmware, and a
>>> /19M vmlinuz.
>>>
>> Yeah, hard numbers to compete with! :-)

I really think comparing our cloud images to theirs is comparing
apples to !apples. The numbers are nice to know what we're competing
against, but don't think we need to have the smallest kernel.

I don't know this for a fact, but I think the Ubuntu EC2 image is
tailored very specifically to run in EC2 only. We don't do this kind
of tailoring in Fedora. One to rule them all.

And CoreOS is very tailored, and has different images for about
everything they run on so it's fair to assume they also have several
different kernel setups. We only want two: core/cloud and full.

> The only way to win is to not play at all? :)
>
> Small note too, just because the vmlinuz are of a certain size does
> not mean they contain similar content.  Without really digging into
> the config settings it's hard to do a true apples to apples
> comparison.  Still, having the overall sizes handy is helpful, thanks.
>
>> I think Josh is mostly there.  He has 58MB + 5M vmlinuz + <similar?>
>> firmwre.
>
> Firmware is owned by linux-firmware, not the kernel package.  I didn't
> include it in my kernel numbers for that reason.
>
>> He just has to cut 35MB or so from /lib/modules/.  We can probably nickel
>> and dime and review a lot of cruft to get there, but what is that 35MB
>> really doing to get us anything?  I am sure half of that can be removed by
>> re-examining the minimal-list he sent (I can even help there).
>
> Right.  Considering the bloat elsewhere in the distro, I think we can
> start with what I have and work from there if needed.

Excellent progress there. So 35MB are already gone and I figure
(re)moving graphics, sound and other obvious things will gain us quite
some more MB. Nice job.

>> Maybe impose only xfs as the fs of choice or some other restrictions and
>> chop it further, but then we lose flexibility.
>
> Oh dear.  Please not another FS thread.  So many emails from last week...
>
>> Instead of competing with Ubuntu on minimalist can we compete on pretty
>> close but a lot more flexible?  Do Ubuntu users have much choice on how
>> they configure their environment?  Or is Fedora Cloud providing a generic
>> cookie cutter installation?
>
> Right, I kind of like that we'd have a smaller core package that is
> still broadly useful.

Exactly. We only offer different images for different purposes
(software stacks), not for different platforms. So every image should
be able to run on all supported platforms.

-- Sandro