[Mesa-dev] Clover clEnqueue* function don't implement blocking?

[Francisco Jerez]

"Dorrington, Albert" <albert.dorrington at lmco.com> writes:

> From reviewing api/transfer.cpp, it looks like all of the API calls that have a blocking parameter do not have anything that implement blocking functionality.
>
> clEnqueueReadBuffer(), clEnqueueWriteBuffer(),
> clEnqueueReadBufferRect(), clEnqueueWriteBufferRect(),
> clEnqueueReadImage(), clEnqueueWriteImage()
> clEnqueueMapBuffer(),
> clEnqueueMapImage()
>
> For all of these functions, shouldn't there be a conditional wait on the event implemented, something like the following?
>
>   auto hev = create<hard_event>(...);
>   ret_object(rd_ev, hev);
>   if (blocking) { hev().wait(); }
>   return CL_SUCCESS;
>
> My initial tests indicate this works, but I'm not sure if I'm missing something in the event handling/cleanup.
>

Nope, that's usually not necessary.  The "blocking" parameter of some
OpenCL entry points surprisingly doesn't imply that the enqueued
operation itself should be blocking, it just determines whether the
application is allowed to reuse the provided memory for other purposes
after the call returns -- and in our implementation that's always the
case because we don't do DMA from client addresses, as we discussed
previously, so we can ignore the blocking parameter most of the time.

Note that this doesn't mean that buffer upload is necessarily
synchronous [buffer download is, though], pipe drivers are free to keep
the written bits in some temporary storage and perform the final copy
asynchronously.

> Al Dorrington
> Software Engineer Sr
> Lockheed Martin, Mission Systems and Training
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
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