commit 0e71e72479f05cfc5635b5bd9765d2f5472e930c
author Andrew Woloszyn <andrew.woloszyn@gmail.com> Wed Dec 11 08:29:49 2024 -0800
committer GitHub <noreply@github.com> Wed Dec 11 11:29:49 2024 -0500
tree b9282b5bd21cf22c96c1b1be557986086f28bad4
parent c31583338a1d8cd099211d8980af7e2dd5791ce5

[hip] Update the hip runtime so that multiple physical devices can back a logical device. (#18790)

This gives us an interface for creating a logical device from a set of
physical hip devices.

Each physical device in the new logical device is represented as a queue in the
logical device and therefore can be accessed by specifying a queue affinity
for operations and buffers.

This is a pretty substantial change to how hip devices are handled. 
In general:
1. Synchronization is updated so that we no longer have to do a CPU round trip
  for GPU<->GPU synchronization.
2. The deferred work queue is no longer in use in HIP at all.
3. We have 2 much simpler helper threads per device. They handle keeping high-cost operations off the main thread. Specifically, async memory operations, and queue executions which are emulated in HIP, and have a relatively high cost.

Signed-off-by: Andrew Woloszyn <andrew.woloszyn@gmail.com>