Re: [Starpu-devel] Problem with performance model calibration

[Samuel Thibault <samuel.thibault@inria.fr>]

Mirko Myllykoski, le ven. 05 juin 2020 14:13:35 +0200, a ecrit:
> As you said, this probably does not matter when scheduling is
> concerned but I can see how it could impact the performance models.

Yes, sure, but we use the performance models *for* the scheduling :)

> I should also mention that I am compiling StarPU with the
> --disable-cuda-memcpy-peer flag enabled. This seems to improve the
> performance (sometimes significantly)

That's surprising. It'd be useful to investigate in traces how you can
get a performance improvement since this option basically adds *more*
synchronization within CUDA.

> I can see how this could cause problems if the CUDA threads is busy
> doing something else while a task starts/finishes.

Yes, that would perturbate performance models a lot since it'd make CUDA
report kernel termination only after some other terminations as well.
Again, the performance model getting affected is actually what we want
since that's what the scheduler will be faced to.

Samuel