[RFC] Drop Non-smp PowerPC Kernel Flavor

Jeremy Kerr jeremy.kerr at canonical.com
Thu Mar 15 03:02:09 UTC 2012

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.



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