[liuliu]

My understanding is that you cannot talk about warp specialization without talking about the alternative: multi-stage pipelining. And the final example code given is multi-stage pipeline with double buffers.

And here is my understanding where it differs:

1. multi-stage pipeline requires careful hand-tuning, even at PTX level to make sure your async wait is weaved properly to maximize overlap.

2. since these register files now is huge, multi-stage pipeline is difficult to write at intrinsics level to make efficient use of these huge register files.

3. Warp specialization delegated most of these scheduling dynamically, hence it is better adapted to hardware (and have more information to make scheduling decisions at runtime). Although this is a bit moot because we write different code for different hardware anyway.

Anything more I am missing?

[rohany]

Author here! I think that warp specialization is inherently related to multi-stage pipelining, they aren't really alternatives of each other. Warp specialization is a way to realize a multi-stage pipeline in the face of hazards that may cause the pipeline to spill out of the register file or not let parts of the pipeline run concurrently as desired.

The fact that we tend to need different warp specialization strategies for different hardware is a consequence of the capabilities of that hardware (i.e. different asynchronous instruction types), and contributes to the complexity of targeting that new hardware.