34028294e4
This patch adds `olGetEventElapsedTime` to the new LLVM Offload API, as requested in [#185728](https://github.com/llvm/llvm-project/issues/185728), and adds the corresponding support in `plugins-nextgen`. A main motivation for this change is to make it possible to measure the elapsed time of work submitted to a queue, especially kernel launches. This is relevant to the intended use of the new Offload API for microbenchmarking GPU libc math functions. ### Summary The new API returns the elapsed time, in milliseconds, between two events on the same device. To support the common pattern `create start event → enqueue kernel → create end event → sync end event → get elapsed time`, `olCreateEvent` now always creates and records a backend event through the device interface. For backends that materialize real event state, this gives the event concrete backend state that can be used for elapsed-time measurement. For backends that do not materialize backend event state, `EventInfo` may still remain null and existing event operations continue to treat such events as trivially complete. Previously, an event created on an empty queue could be represented only as a logical event. That representation was sufficient for sync and completion queries, but it was not suitable for elapsed-time measurement because there was no backend event state to timestamp. The new behavior preserves the meaning of completion of prior work while also allowing backends with timing support to attach real event state. ### Changes in `plugins-nextgen` #### Common interface Add elapsed-time support to the common device and plugin interfaces: * `GenericPluginTy::get_event_elapsed_time` * `GenericDeviceTy::getEventElapsedTime` * `GenericDeviceTy::getEventElapsedTimeImpl` #### AMDGPU * Add the required ROCr declarations and wrappers. * Enable queue profiling at queue creation time. * Record events by enqueuing a real barrier marker packet on the stream. * Retain the timing signal needed to query the recorded marker later. * Implement `getEventElapsedTimeImpl` using `hsa_amd_profiling_get_dispatch_time`, converting the result to milliseconds with `HSA_SYSTEM_INFO_TIMESTAMP_FREQUENCY`. This follows the ROCm/HIP approach of enabling queue profiling at HSA queue creation time, while keeping the AMDGPU queue path simpler than the lazy-enable alternative discussed during review. #### CUDA * Add the required CUDA driver declarations and wrappers. * Implement `getEventElapsedTimeImpl` with `cuEventElapsedTime`. #### Host * Add `getEventElapsedTimeImpl` that stores `0.0f` in the output pointer, when present, and returns success. Reason: the host plugin does not materialize backend event state and already treats event operations as trivially successful. Returning `0.0f` preserves that model without introducing a new failure mode. #### Level Zero * Add `getEventElapsedTimeImpl`, but leave it unimplemented. Reason: the Level Zero plugin currently does not provide standalone backend event support for this event model. For example, `waitEventImpl` / `syncEventImpl` are still unimplemented there. --------- Signed-off-by: Leandro Augusto Lacerda Campos <leandrolcampos@yahoo.com.br> Signed-off-by: Leandro A. Lacerda Campos <leandrolcampos@yahoo.com.br>
Liboffload
This directory contains the implementation of the work-in-progress new API for Offload. It builds on top of the existing plugin implementations but provides a single level of abstraction suitable for implementation of many offloading language runtimes, rather than just OpenMP.
Testing liboffload
The main test suite for liboffload can be run with the check-offload-unit
target, which runs the offload.unittests executable. The test suite will
automatically run on every available device, but can be restricted to a single
platform (CUDA, AMDGPU) with a command line argument:
$ ./offload.unittests --platform=CUDA
Tracing of Offload API calls can be enabled by setting the OFFLOAD_TRACE
environment variable. This works with any program that uses liboffload.
$ OFFLOAD_TRACE=1 ./offload.unittests
---> olInit(nullptr)-> OL_SUCCESS
# etc
The host plugin is not currently supported.
Modifying liboffload
The main header (OffloadAPI.h) and some implementation details are
autogenerated with tablegen. See the API definition README
for implementation details.