[SYCL] Add improved host task extension #13339
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Introduce a new extension which extends the host task interfaces to allow host task functions to enqueue asynchronous backend-specific commands and connect these commands with the SYCL DAG. This is done in two parts: Firstly to introduce an interface; `handler::get_native_events`, which is enabled by a property; `manual_interop_sync`, which allows users to retrieve native events which would ordinarily be synchronized with before the host task function is executed, having these instead handled by the the host task function, as dependencies to an asynchronous backend API. Secondly to introduce an interface; `handler::add_native_events` which allows users to add additional native events which are produced from an asynchronous backend API, to then be encapsulated in the SYCL event returned by `submit`.
| events to be passed to the host task function instead, allowing the host task | ||
| function to be invoked without requiring full completion of said incoming | ||
| events. This extension also introduces an interface which allows those native | ||
| vents to be retrieved from within the host task function. |
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| vents to be retrieved from within the host task function. | |
| events to be retrieved from within the host task function. |
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| _Effects_: Returns a `std::vector` of the native events for the backend | ||
| `Backend` for the dependencies for the dependencies to the host task command if |
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| `Backend` for the dependencies for the dependencies to the host task command if | |
| `Backend` for the dependencies to the host task command if |
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| cl_event ne2; | ||
| clEnqueueReadBuffer(queue, mem, CL_FALSE, 0, sizeof(int), &pattern, 1, | ||
| &nativeEvent1, &ne2); |
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| &nativeEvent1, &ne2); | |
| &ne1, &ne2); |
| to an OpenCL command queue asynchronously. The OpenCL event which results from | ||
| enqueueing these commands is then converted to a SYCL `event` via the backend | ||
| interop interface. Then the created SYCL `event` is passed to the host task via | ||
| `interop_handle::ext_oneapi_add_event`. |
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| `interop_handle::ext_oneapi_add_event`. | |
| `interop_handle::ext_oneapi_add_native_events`. |
| [source,c++] | ||
| ---- | ||
| template <backend Backend> | ||
| std::vector<backend_return_t<Backend, event>> ext_oneapi_get_native_events(); |
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| std::vector<backend_return_t<Backend, event>> ext_oneapi_get_native_events(); | |
| std::vector<backend_return_t<Backend, native_event>> ext_oneapi_get_native_events(); |
event will give people the wrong assumption that it is sycl::event
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| template <backend Backend> | ||
| void ext_oneapi_add_native_events( | ||
| backend_return_t<Backend, event> hostTaskEvent); |
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| backend_return_t<Backend, event> hostTaskEvent); | |
| backend_return_t<Backend, native_event> hostTaskEvent); |
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| template <backend Backend> | ||
| void ext_oneapi_add_native_events( | ||
| const std::vector<backend_return_t<Backend, event>> &hostTaskEvents) |
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| const std::vector<backend_return_t<Backend, event>> &hostTaskEvents) | |
| const std::vector<backend_return_t<Backend, native_event>> &hostTaskEvents) |
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| As the SYCL `event` that is returned from the submission of the host task is | ||
| created before the host task function is executed, it is necessary for the | ||
| SYCL `event`(s) passed to `ext_oneapi_add_native_events` be stored in a place |
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| SYCL `event`(s) passed to `ext_oneapi_add_native_events` be stored in a place | |
| native event(s) passed to `ext_oneapi_add_native_events` be stored in a place |
| created before the host task function is executed, it is necessary for the | ||
| SYCL `event`(s) passed to `ext_oneapi_add_native_events` be stored in a place | ||
| accessible to the `event`, and access to this location must be provided to the | ||
| `interop_handle` so that SYCL `events` added from the host task function can be |
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| `interop_handle` so that SYCL `events` added from the host task function can be | |
| `interop_handle` so that native events added from the host task function can be |
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| cgh.host_task([&](sycl::interop_handle &ih, {ext::oneapi::experimental}) { | ||
| // Dependent events are returned to be synchronized with. | ||
| auto nativeEvents = ih.get_native_events<backend::opencl>(); |
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where do nativeEvents come from, from line 178 ih.ext_oneapi_add_native_events<backend::opencl>(ne2); of the last host_task?
If the answer is yes, how about host_task1 --> sycl kernel --> host_task2, actually, the host_task2 does not depend on the host_task1, but depends on sycl kernel, so, we don't need the waiting events in line 270, the dependency is handled in line 256.
Even for the case host_task1 --> host_task2, since the native event in host_task1 is wrapped as sycl::event, and so for host_task2, line 256 is enough, we don't need the waiting events at line 270.
Looks that get_native_events is not necessary.
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| // The event returned by the host task function are waiting on by the event | ||
| // returned by submit | ||
| ih.ext_oneapi_add_native_events<backend::opencl>(ne2); |
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for a corner case that there are several native events generated and they are independent.
ih.ext_oneapi_add_native_eventsbackend::opencl(nes);
Is it possible for e2 to represent all the native events in nes? My understanding is that e2 is just a wrapper of one native event.
| includes both asynchronous commands executing before the the host task which the | ||
| host task depends on, and asynchornous commands executing after the host task |
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| includes both asynchronous commands executing before the the host task which the | |
| host task depends on, and asynchornous commands executing after the host task | |
| includes both asynchronous commands executing before the host task which the | |
| host task depends on, and asynchronous commands executing after the host task |
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Introduce a new extension which extends the host task interfaces to allow host task functions to enqueue asynchronous backend-specific commands and connect these commands with the SYCL DAG.
This is done in two parts:
Firstly to introduce an interface;
handler::get_native_events, which is enabled by a property;manual_interop_sync, which allows users to retrieve native events which would ordinarily be synchronized with before the host task function is executed, having these instead handled by the the host task function, as dependencies to an asynchronous backend API.Secondly to introduce an interface;
handler::add_native_eventswhich allows users to add additional native events which are produced from an asynchronous backend API, to then be encapsulated in the SYCL event returned bysubmit.This extension is implemented in #12921