[Static Runtime] Avoid copying function objects per StaticRuntime instance (#68368)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68368
Currently, each instance of `StaticRuntime` has its own copy of `std::function` object wrapped in `ProcessedNode::Function` object, in order to invoke actual operation implementation.
However, all instances of `StaticRuntime` derived from same `StaticModule` objects invoke exactly same op implementation, and this is avoidable.
This change adds `StaticModule::functions_` member variable to keep a list of unique instance of `ProcessedFunction` objects. A newly constructed `StaticRuntime` takes `ProcessedFunction`'s pointers instead of the whole function object. This can save a substantial amount of memory per `StaticRuntime` instance.
This comes with a sacrifice in execution time. Now that a `ProcessedNode` instance keeps the function object's pointer, executing a node now involves an extra pointer dereference. However, this cost was proved to be negligible from local performance tests.
Thanks to hlu1 for proposing this non-intrusive improvement idea :D
Test Plan:
This change reduces the size of a StaticRuntime instance by 14.41% (459KB -> 393KB) (patched D32181666 to print the memory turnover from instantiating a StaticRuntime instance) for CMF/local ( & 8% for CMF/local_ro). No noticeable latency regression was observed.
==AFTER
* CMF/local
memory turnover: 393608
latency: PyTorch run finished. Milliseconds per iter: 15.6965. Iters per second: 63.7087
* CMF/local_ro
memory turnover:387288
latency: PyTorch run finished. Milliseconds per iter: 7.51308. Iters per second: 133.101
==BEFORE
* CMF/local
memory turnover: 459888
latency: PyTorch run finished. Milliseconds per iter: 15.8278. Iters per second: 63.18
* CMF/local_ro
memory turnover: 420832
latenfcy: PyTorch run finished. Milliseconds per iter: 7.43756. Iters per second: 134.453
==Confirmation that ptvsc2_predictor_bench reports the same memrmoy management stats for inline_cvr:
==AFTER
Total number of managed tensors: 2660
Total number of managed output tensors: 0
Total number of unmanaged values: 3041
Total memory managed: 1496896 bytes
Total number of reused tensors: 1183
Total number of 'out' variant nodes/total number of nodes: 2452/2469 (99.3115%)
Total number of managed tensors: 1412
Total number of managed output tensors: 0
Total number of unmanaged values: 2677
Total memory managed: 39040 bytes
Total number of reused tensors: 959
Total number of 'out' variant nodes/total number of nodes: 1928/1937 (99.5354%)
Total number of managed tensors: 1293
Total number of managed output tensors: 0
Total number of unmanaged values: 14
Total memory managed: 5293824 bytes
Total number of reused tensors: 771
Total number of 'out' variant nodes/total number of nodes: 1298/1298 (100%)
==BEFORE
Total number of managed tensors: 2660
Total number of managed output tensors: 0
Total number of unmanaged values: 3041
Total memory managed: 1496896 bytes
Total number of reused tensors: 1183
Total number of 'out' variant nodes/total number of nodes: 2452/2469 (99.3115%)
Total number of managed tensors: 1412
Total number of managed output tensors: 0
Total number of unmanaged values: 2677
Total memory managed: 39040 bytes
Total number of reused tensors: 959
Total number of 'out' variant nodes/total number of nodes: 1928/1937 (99.5354%)
Total number of managed tensors: 1293
Total number of managed output tensors: 0
Total number of unmanaged values: 14
Total memory managed: 5293824 bytes
Total number of reused tensors: 771
Total number of 'out' variant nodes/total number of nodes: 1298/1298 (100%)
Reviewed By: swolchok
Differential Revision: D32337548
fbshipit-source-id: e714e735399c93fde337b0f70e203a2de632057a
pytorch
aa9ee8d0 - [Static Runtime] Avoid copying function objects per StaticRuntime instance (#68368)
