Re: Which kernel flavor for big.Little systems?
On Wednesday 07 May 2014 12:23:10 Lennart Sorensen wrote:
> On Wed, May 07, 2014 at 04:03:04PM +0100, David Goodenough wrote:
> > The world of big.Little is about to hit boards that Debian might support
> > in the form of the AllWiner A80 (it has 4 big A15 and 4 little A7
> > processors). This is due to hit the marketplace in the form of PcDuino-8
> > and
> > Cubieboard-8 boards next month. The A80 Optimus board is supposed to
> > be available this month.
> >
> > Which kernel flavor should be used? Should it just be treated as a
> > 64 bit ARM board, or are all ARM 64 kernels going to be big.Little enabled
> > in rather the same way that Amd64 kernels are today - although of course
> > in the Amd64 world this only applies to the application code not the
> > kernel? If so I would then be able to load either an armhf or an arm64
> > deb file and run the relevant executables I presume.
>
> Well A15/A7 are 32bit (with LPAE for >32bit physical memory). They are
> not 64bit.
>
> A53/A57 chips are 64bit.
>
> I think the vexpress in the mp kernel is already A15 based, so probably
> the same kernel would make sense.
>
> I am not sure there is any support for big.LITTLE in the current kernel
> though, although it is certainly being worked on.
Well thank you for clearing up my mis-understanding about the big in
big.Little. Being all 32 bit obviously makes life easier, in that all
the apps will be armhf, which should mean it fits into the current
Debian family without real change (other than the kernel).
It will be interesting to see what kernel bits AllWinner release with
the A80 and what then gets merged into the mainline kernel. Although
I suppose I should not hold my breath for that as the AllWinner kernel
shipped with the Cubieboard2 is only single processor, it does not even
make use of SMP.
David
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