Re: Candidate Linux ABI for Intel AMX and hypothetical new related features

Len,

On Thu, May 20 2021 at 17:49, Len Brown wrote:

On Thu, May 20, 2021 at 5:41 PM Thomas Gleixner [off-list ref] wrote:

quoted

  2) It has effects on power/thermal and therefore effects which reach
     outside of the core scope

FWIW, this is true of *every* instruction in the CPU.
Indeed, even when the CPU is executing *no* instructions at all,
the C-state chosen by that CPU has power/thermal impacts on its peers.

Granted, high performance instructions such as AVX-512 and TMUL
are the most extreme case.

Right and we have to draw the line somewhere.

quoted

  3) Your approach of making it unconditionally available via the
     proposed #NM prevents the OS and subsequently the system admin /
     system designer to implement fine grained control over that
     resource.

     And no, an opt-in approach by providing a non-mandatory
     preallocation prctl does not solve that problem.

I'm perfectly fine with making the explicit allocation (aka opt-in) mandatory,
and enforcing it.

Great!

Thanks,

        tglx