Dual View Tool Events

[DavidPoliakoff]

This PR adds Dual View events to the callback interface, and implements them. Current signature (up for debate) are events on sync and modify that pass

1. The name of the view (const char*)
2. The beginning of the allocation (const void* const)
3. Whether the sync/modify was on the device side (bool: true means on device)

Questions I have for reviewers (other than "should this go in")

1. Right now we pass the host View name if the sync/modify is on the host, device view name otherwise. I could see it being smart to pass the same name to both events, though I decided not to. Game to hear other opinions though
2. Are these the only events that matter (pretty sure yes but I don't know Dual Views)?

[stanmoore1]

Yes!!! I've wanted this for forever, see kokkos/kokkos-tools#11.

[DavidPoliakoff]

@stanmoore1 , Stan, we're exactly on the same page, I'm just about two years slower. I'm going back through the Kokkos Tools backlog, but we should also have a conversation about anything you want done in the Tools area. The roadmap, fyi:

1. This
2. "FakeCuda" memory space (actually host memory, but differentiable by tools as a different MemorySpace)
3. Memory sampling plus profiling

"If I see an access on the Host copy after a change on the device copy without a sync in the middle" kinds of rules start to become possible. Now I know you've been there for years, but we're catching up!

[crtrott]

Please document first what this does. The bool state isn't clear to me. Like why is "onDevice" false when it needed to sync to the host? And why is it true when syncing to the device? I mean what if it is in a valid state either way and so need_sync would be false for both host and device? Is the bool just to mean that foo in sync_foo or modify_foo was device if it is true?

[DavidPoliakoff]

@crtrott

Is the bool just to mean that foo in sync_foo or modify_foo was device if it is true?

Yes. Do we want a different name, do we want an enum, or what?

[crtrott]

If we just get a comment on the functions what the arguments mean and maybe rename in the sync version the on_device to to_device I am fine.

[DavidPoliakoff]

@crtrott, handled via 87c5b2d , if this passes CI