Task Pooling

[erincatto]

I wonder if enkiTS should provide task pooling. On the C side enkiCreateTaskSet calls _aligned_malloc by default. It would be nice to see some pooling used.
Pooling is a bit tricky for the user because ICompletable cannot be copied. This prevents the use of standard containers like std::vector.

I guess this doesn't work in C++ since users can derive from ITaskSet, etc. Perhaps the task system could call a method on ICompletable to inform the task that it may be returned to a user task pool.

[dougbinks]

I don't think enkiTS itself should provide task pooling, as this can be provided in user space with no loss of performance/flexibility and enkiTS is itself designed to be lightweight.

Whilst ICompletable cannot be copied, arrays can be constructed from which pools can be managed and there are ways around using non-copyable objects in the standard containers, for example using pointers rather than the object itself.

The C side does allocate single tasks, and perhaps an improved interface would be to allow arrays of enkiTaskSet* to be allocated.

Note that applications should in general try to keep the number of tasks down and use the ITaskSet m_SetSize to perform data parallelism where appropriate.

I can see the benefit of adding an example, or perhaps even an external library which can be used for this.

[erincatto]

I agree that on the C++ side the user should do pooling. And I agree that enkiTS should not see a large number of tasks.

On the C side the only option is the custom allocator. Which could be an arena allocator in some cases. So maybe that is not a big problem.

Task allocation becomes a bit more complex when binding a library's generic task API to enkiTS. For example, Box2D is issuing some unknown number of tasks that the user has to bind to enkiTS tasks. This is where pooling becomes important.

I think enkiTS users would find an example of task pooling and maybe an arena allocator valuable. I might be able to help out with this as I refine the Box2D task API.

[dougbinks]

It would be great to see the Box2D task API and have a think about how to make it easier to use with enkiTS. I'm a bit wary of adding any functionality which can be layered on top though, but if there's a way I can extend the API to make certain use cases easier then I will take a look.