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214: Rewrite GpuFuture to avoid blocking and to use less space r=kvark a=lachlansneff Since `GpuFuture` doesn't blocking wait for the mapping to resolve anymore, we need to poll the device for it to actually work. ~~I haven't added that to the `hello-compute` example, so it doesn't work anymore.~~ Co-authored-by: Lachlan Sneff <lachlan.sneff@gmail.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,72 +1,94 @@ | ||
| use std::future::Future; | ||
| use std::pin::Pin; | ||
| use std::sync::{Arc, Mutex}; | ||
| use std::sync::Arc; | ||
| use std::task::{Context, Poll, Waker}; | ||
| use parking_lot::Mutex; | ||
| use crate::BufferAddress; | ||
|
|
||
| struct GpuFutureInner<T> { | ||
| id: wgc::id::DeviceId, | ||
| result: Option<T>, | ||
| waker: Option<Waker>, | ||
| enum WakerOrResult<T> { | ||
| Waker(Waker), | ||
| Result(T), | ||
| } | ||
|
|
||
| /// A Future that can poll the wgpu::Device | ||
| pub struct GpuFuture<T> { | ||
| inner: Arc<Mutex<GpuFutureInner<T>>>, | ||
| data: Arc<Data<T>>, | ||
| } | ||
|
|
||
| pub enum OpaqueData {} | ||
|
|
||
| struct Data<T> { | ||
| buffer_id: wgc::id::BufferId, | ||
| size: BufferAddress, | ||
| waker_or_result: Mutex<Option<WakerOrResult<T>>>, | ||
| } | ||
|
|
||
| /// A completion handle to set the result on a GpuFuture | ||
| pub struct GpuFutureCompletion<T> { | ||
| inner: Arc<Mutex<GpuFutureInner<T>>>, | ||
| data: Arc<Data<T>>, | ||
| } | ||
|
|
||
| impl<T> Future for GpuFuture<T> | ||
| { | ||
| type Output = T; | ||
|
|
||
| fn poll(self: Pin<&mut Self>, context: &mut Context) -> Poll<Self::Output> { | ||
| // grab a clone of the Arc | ||
| let arc = Arc::clone(&self.get_mut().inner); | ||
| let mut waker_or_result = self.into_ref().get_ref().data.waker_or_result.lock(); | ||
|
|
||
| // grab the device id and set the waker, but release the lock, so that the native callback can write to it | ||
| let device_id = { | ||
| let mut inner = arc.lock().unwrap(); | ||
| inner.waker.replace(context.waker().clone()); | ||
| inner.id | ||
| }; | ||
|
|
||
| // polling the device should trigger the callback | ||
| wgn::wgpu_device_poll(device_id, true); | ||
|
|
||
| // now take the lock again, and check whether the future is complete | ||
| let mut inner = arc.lock().unwrap(); | ||
| match inner.result.take() { | ||
| Some(value) => Poll::Ready(value), | ||
| _ => Poll::Pending, | ||
| match waker_or_result.take() { | ||
| Some(WakerOrResult::Result(res)) => Poll::Ready(res), | ||
| _ => { | ||
| *waker_or_result = Some(WakerOrResult::Waker(context.waker().clone())); | ||
| Poll::Pending | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<T> GpuFutureCompletion<T> { | ||
| pub fn complete(self, value: T) { | ||
| let mut inner = self.inner.lock().unwrap(); | ||
| inner.result.replace(value); | ||
| if let Some(waker) = &inner.waker { | ||
| waker.wake_by_ref(); | ||
| let mut waker_or_result = self.data.waker_or_result.lock(); | ||
|
|
||
| match waker_or_result.replace(WakerOrResult::Result(value)) { | ||
| Some(WakerOrResult::Waker(waker)) => waker.wake(), | ||
| None => {} | ||
| Some(WakerOrResult::Result(_)) => { | ||
| // Drop before panicking. Not sure if this is necessary, but it makes me feel better. | ||
| drop(waker_or_result); | ||
| unreachable!() | ||
| }, | ||
| }; | ||
| } | ||
|
|
||
| pub(crate) fn to_raw(self) -> *mut OpaqueData { | ||
| Arc::into_raw(self.data) as _ | ||
| } | ||
|
|
||
| pub(crate) unsafe fn from_raw(this: *mut OpaqueData) -> Self { | ||
| Self { | ||
| data: Arc::from_raw(this as _) | ||
| } | ||
| } | ||
|
|
||
| pub(crate) fn get_buffer_info(&self) -> (wgc::id::BufferId, BufferAddress) { | ||
| (self.data.buffer_id, self.data.size) | ||
| } | ||
| } | ||
|
|
||
| pub(crate) fn new_gpu_future<T>(id: wgc::id::DeviceId) -> (GpuFuture<T>, GpuFutureCompletion<T>) { | ||
| let inner = Arc::new(Mutex::new(GpuFutureInner { | ||
| id, | ||
| result: None, | ||
| waker: None, | ||
| })); | ||
| pub(crate) fn new_gpu_future<T>( | ||
| buffer_id: wgc::id::BufferId, | ||
| size: BufferAddress, | ||
| ) -> (GpuFuture<T>, GpuFutureCompletion<T>) { | ||
| let data = Arc::new(Data { | ||
| buffer_id, | ||
| size, | ||
| waker_or_result: Mutex::new(None), | ||
| }); | ||
|
|
||
| ( | ||
| GpuFuture { | ||
| inner: inner.clone(), | ||
| data: Arc::clone(&data), | ||
| }, | ||
| GpuFutureCompletion { inner }, | ||
| GpuFutureCompletion { data }, | ||
| ) | ||
| } |
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