Re: [atomic-devel] ARM builds?

[Richard Henwood <Richard Henwood arm com>]

> -----Original Message-----
> From: SGhosh [mailto:sghosh redhat com]
> Sent: Saturday, August 27, 2016 8:18 AM
> To: Josh Berkus; Jon Stanley; Richard Henwood
> Cc: atomic-devel
> Subject: Re: [atomic-devel] ARM builds?
>
> On 08/26/2016 06:13 PM, Josh Berkus wrote:
> > On 08/26/2016 11:24 AM, Jon Stanley wrote:
> >> Will kube schedule a container on a host that can't run it? i.e. a
> >> container with x86 code on a AArch64 host, or vice versa? I think
> >> that it needs to DTRT sooner rather than later if the scheduling
> >> isn't smart yet. In the meantime I assume that you could run a
> >> separate cluster of ARM vs. x86, but that would probably be less than
> >> ideal I think. Other thoughts?
> > Oh, I wasn't even thinking of mixed clusters.  Figured it wouldn't be
> > possible.   Also, while I can imagine having an x86 kube-master and a
> > bunch of ARM kubelets, I'm not sure that there's much of a real cases
> > for mix-and-match kubelets.
> >
> In general if you think of a datacenter of mixed architecture, you would want a
> global resource allocator that is architecture aware. Making architecture-
> specific clusters reduces your flexibility in making resource allocation decisions.
>
> In the virt world there has been a tendency to create cluster of a like
> architecture - where arch is actually a very particular x86 cpu family/generation.
> This was required for VM migration flexibility and the need to map VM CPU
> capabilities to the host CPU capabilities. For containers, that CPU mapping need
> does not exist - so the clusters can be more diverse.
>
> The current state of Kube however is not arch aware afaik - although we could
> manage that via node labels, it would be clunky. So short term, arch specific
> clusters. But the goal should be arch-aware orchestrators.
>

Thanks for the info: labels may get us being able to demo some things. I share your vision of arch-aware orchestrators as integrated system logic in the medium-term.

> Note: container naming/packaging in general is not architecture aware either.
> Docker Hub packages are mixed arch, even though Docker recommends using
> different registries for different archs. The RH container image naming
> standards that leverages container labels embeds an arch label for all the
> Fedora/RH/CentOS images. Skopeo can inspect those labels remotely. But there
> is more work to be done at the community level for arch awareness.
>

Indeed: repositories need some arch-specific-ness to enable the heterogeneous container datacenter. From the recent Fedora Flock (reading about it here: http://lwn.net/Articles/697347/) it seems that architecture is anticipated in Fedora's Layered Docker Image Build Service, which sounds like things are headed in the right direction.

Best regards,
Richard

PS. I have made some progress with an AArch64 Atomic Host F24 build it's not booting yet. Debugging...
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