pytorch

10b40acb - [PyTorch][Static Runtime] Fast aliasing in select_tensor by manual borrowing (#68122)

[PyTorch][Static Runtime] Fast aliasing in select_tensor by manual borrowing (#68122) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/68122 See code comments for details; in brief, we repurpose support for borrowing `Tensor`s in `MaybeOwned` to make the `select_tensor` output a borrowed IValue that we have to clean up manually. If we have any other ops that always create a new reference to an existing Tensor, we can easily apply this same optimization. ghstack-source-id: 146482212 Test Plan: See perf measurements on ctr_mobile_feed local_ro net for this stack: P467203421 (local is neutral: P467267554) --do_profile output for local_ro (updated Dec 10): ``` swolchok@devbig032 /d/u/s/f/fbcode> tail Stable.profile.txt First iter time: 0.989023 ms Number of operators: 2037 Total number of managed tensors: 1597 Total number of managed output tensors: 0 Total number of unmanaged values: 2568 Number of unmanaged values requiring cleanup: 2568 Number of unmanaged values not requiring cleanup: 0 Total memory managed: 50368 bytes Total number of reused tensors: 1010 Total number of 'out' variant nodes/total number of nodes: 2001/2037 (98.2327%) swolchok@devbig032 /d/u/s/f/fbcode> ttail TMCC^C swolchok@devbig032 /d/u/s/f/fbcode> tail TMCOFastAliasing.profile.txt First iter time: 0.994703 ms Number of operators: 2551 Total number of managed tensors: 1146 Total number of managed output tensors: 0 Total number of unmanaged values: 4047 Number of unmanaged values requiring cleanup: 3533 Number of unmanaged values not requiring cleanup: 514 Total memory managed: 50048 bytes Total number of reused tensors: 559 Total number of 'out' variant nodes/total number of nodes: 2001/2551 (78.4398%) ``` for local: (also Dec 10): ``` ==> Stable.local.profile.txt <== First iter time: 9.0909 ms Number of operators: 1766 Total number of managed tensors: 1894 Total number of managed output tensors: 0 Total number of unmanaged values: 2014 Number of unmanaged values requiring cleanup: 2014 Number of unmanaged values not requiring cleanup: 0 Total memory managed: 4541440 bytes Total number of reused tensors: 847 Total number of 'out' variant nodes/total number of nodes: 1744/1766 (98.7542%) ==> TMCOFastAliasing.local.profile.txt <== First iter time: 7.5512 ms Number of operators: 2378 Total number of managed tensors: 1629 Total number of managed output tensors: 0 Total number of unmanaged values: 3503 Number of unmanaged values requiring cleanup: 2891 Number of unmanaged values not requiring cleanup: 612 Total memory managed: 3949312 bytes Total number of reused tensors: 586 Total number of 'out' variant nodes/total number of nodes: 1744/2378 (73.3389%) ``` Reviewed By: hlu1 Differential Revision: D32318674 fbshipit-source-id: a2d781105936fda2a3436d32ea22a196f82dc783