Re: Summary of the ARM ports BoF at DC15
On Sat, 2015-09-12 at 23:26 +0100, Wookey wrote:
> +++ Ian Campbell [2015-09-12 15:55 +0100]:
>
> > The other two subarches in the kernel are orion5x and versatile. I
> have
> > no personal interest in either. My gut suggests that orion5x (the
> > Marvell variant prior to kirkwood) is the one people might more
> > plausibly still be interested in, but I don't know that any is
> actually
> > still using it.
>
> I think versatile is mostly there because it's the standard QEMU
> target. So it's useful if you need armel under qemu-system. Not sure
> if this has changed (and I may be confused on this matter).
That sounds likely, yes.
I don't know how much need there is for armel under qemu-system these
days though.
> > How much multithreading is there actually in building packages I
> wonder.
>
> Anything using java failed to build on qemu (no multithreading) so
> that may be an area where it happens (if java uses the offending
> instructions for its thread support). And for other things I guess
> they will build, but any thread-using tests will fail.
I was assuming emulation support in the kernel, so I think they should
"work" but more slowly.
The question is how much more slowly in practice and is it so slow as
to be a problem. It may not really matter if e.g. swp emulation is,
say, 1,000x slower than running the instruction natively on h/w if only
1 in every 100,000 userspace instructions run on a buildd is a swp
instruction. It'll make things slower, for sure, but too slow, I don't
know. I think we'll have to wait and see. IMHO there's too many
variables to have a sensible guess.
Ian.
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