Enable cuda graphs for dynamic shapes (#105064)
The general idea is to do a separate CUDA graph for each size. Because of cuda graph trees, these graphs will all share the same memory pool, so your memory usage will only be the worst case memory usage of the biggest dynamic size you want. This requires an extra dispatch in the cudagraphified callable. You must pay for a CUDA graph recording for every dynamic size you encounter, but this is MUCH cheaper than running the entire PT2 compile stack, so I expect you to still see benefits.
This was surprisingly easy to do.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105064
Approved by: https://github.com/voznesenskym
