[Mesa-dev] [PATCH 7/7] softpipe: add support for compute shaders.

[Dave Airlie]

On 27 April 2016 at 11:00, Dave Airlie <airlied at gmail.com> wrote:
>>> So far I've set the execmask to 1 active channel, I'm contemplating
>>> changing that
>>> though and using less machines.
>> Ah yes, I think that would indeed be desirable.
>
> I'll look into it, though it's not that trivial, since you might have a 1x20x1
> layout, also having to make sure each thread gets the correct system values.
>
>>
>>>
>>> Any ideas how to implement this in llvm? :-) 1024 CPU threads?
>> I suppose 1024 is really the minimum work size you have to support?
>> But since things are always run 4-wide (or 8-wide) that would "only" be
>> 256 (or 128) threads. That many threads sound a bit suboptimal to me
>> (unless you really have a boatload of cpu cores), but why not - I
>> suppose you can always pause some of the threads, not all need to be
>> active at the same time.
>> Though I wonder what the opencl-on-cpu guys do...
>
> pocl appears to spawn a number of threads and split the work out amongst
> them in the X direction.
>
> However I'm not seeing how they handle barriers, or if they handle
> them correctly at all.

Okay newer versions of pocl seem to have some sort of thread scheduler,
that schedule workgroups across up to 8 threads, however I can't see how
they deal with barriers still.

Dave.