re: mips64eb seems to be mostly 32-bit

cc: christos directly, he did most of the mipsn64 build work.

> > > The odd thing is, whilst the kernel is aware that the CPU is 64-bit,
> > > the userspace binaries from the install sets are 32-bit. The same
> > > stands for the binaries that come from pkgsrc and for the binaries
> > > compiled from C code natively on the system. Is there a fundamental
> > > reason for this, or is this a build system issue?  
> > 
> > this is normal.
> > 
> > the binaries are 32-bit but require a 64-bit CPU, as they rely
> > upon 64 bit registers existing, but run in a 32-bit address
> > space, which generally reduces the memory requirements for the
> > same task, and often the performance is the same (since the
> > native 64-bit maths operations are available) or even better,
> > and sometimes worse.
> > 
> > we are starting to prepare a pure-64 bit mips system, but it
> > is still not quite ready for general usage (if you notice that
> > -current/HEAD builds now include "mipsn64*" builds.  note the
> > 'n' in the middle.  but these aren't for netbsd 9.x releases,
> > and will hopefully be properly working for netbsd 10.x.)
>
> Thank you for the comments Matthew. I understand n32 userspace is the
> intended arrangement for mips64eb, which until recently was the only
> build with Octeon kernel. Until you explained it, I didn't notice the
> appearance of n64 builds, one of which seems to support Octeon too.
>
> I also understand the n64 builds resemble OpenBSD/octeon (which is
> fully 64-bit). The mipsn64eb directory index does not include X11, but

X11 should appear in the next builds.  we had disabled it while
it wasn't building yet, but is now done.

> seems to include all the files my setup requires. The additional binary
> packages would need to be built on the system, of course. I hope
> pkgsrc-2021Q2 is good enough for that. Other than that, are you aware of
> any particular issues that would make mipsn64eb unsuitable for compiling
> and running C programs over SSH?

i don't know of any particular issues, but i haven't played with this
part yet and we only just recently enabled the builds.  you might be
the first user to try :-)

> The system (a Buildbot worker) is going to run from USB storage, and it
> would be nice to be able to move the storage between E100 and E300
> devices as required. As the best support for Octeon seems to be in
> NetBSD-current only, the system is going to run on snapshots until the
> 10.0 release regardless if the userspace is n32 or n64. Please correct
> me if this is not the case.

this seems right.

> This way, if I have to choose between two snapshots anyway and if
> mipsn64eb is already viable for C userspace development and you think
> it would be more useful to run another test system in n64 rather than
> n32, I can try switching to mipsn64eb to see how it goes. Let me know
> what you think.

certainly we are very interested in making this work properly,
so any testing you run is going to help.

thanks!


.mrg.