Re: [Opengcd-discuss] missing features in gcd/xdispatch

[Mark H. <ma...@he...>]

On Thu, Feb 21, 2013 at 1:20 AM, David Minor <Dav...@or...>wrote:

>  Hello Everyone,****
>
> I just finished a comparative study of xdispatch , boost::asio, Intel TBB
> and c++11 thread constructs. What I did was write multiple implementations
> of an OpenCL based data-flow scheduler.  As a result of this project I
> discovered a few things missing in gcd.  ****
>
> **1.       **The ability to get the number of items currently waiting on
> a queue.  This is important for load-balancing.
>
****
>
> **2.       **A way to create thread-specific data. GCD has queue specific
> data, but since a queue isn’t bound to a thread it’s not the same thing. I
> found this to be important for efficiently doing task parallelism on GPU’s,
> where the GPU driver itself can handle multiple streams, but those streams
> need to be bound to threads.****
>
> **3.       **A way to limit the number of threads that a work item can be
> dispatched on.  This is also relevant to GPU operations, where (at least on
> Nvidia) you want a thread per “real” GPU core and a stream (or OpenCL
> queue) attached to each core.****
>
> ** **
>
> My question is whether it is worth my while to make these changes and try
> to get them accepted and what is the procedure, forums etc. Where these
> issues can be discussed. I don’t want to do this work unless there is some
> sort of consensus on acceptance.  Considering that Apple is driving GCD, I
> don’t expect much of a hearing, but I imagine the xdispatch community would
> be more receptive.  Some of these issues (like queue size) can only be
> resolved at the GCD level, but others could conceivably be implemented as
> xdispatch features.****
>
> OpenGCD and xdispatch are based on an old version of GCD from MacOS 10.6
(IIRC). There has been some development upstream related to integration
with OpenCL:

https://developer.apple.com/library/mac/#documentation/Performance/Conceptual/OpenCL_MacProgGuide/UsingGCDwOpenCL/UsingGCDwOpenCL.html#//apple_ref/doc/uid/TP40008312-CH13-SW1

I suggest you start by contacting the libdispatch mailing list and see what
they say about these topics. Unfortunately, I have not done anything
GPU-related and can't comment on what you are proposing.

Regards,

 - Mark