[Prototype] [PyTorch Edge] Speed up model loading by 12% by directly calling the C file API from FileAdapter (#61997)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61997
After profiling the model loading latency on AI Bench (Android Galaxy S8 US), it seems like a significant amount of time was spent reading data using FileAdapter, which internally calls IStreamAdapter. However, IStreamAdapter uses `std::istream` under the hood, which is not that efficient. This change reduces the model loading time from [~293ms](https://www.internalfb.com/intern/aibench/details/600870874797229) to [~254ms](https://www.internalfb.com/intern/aibench/details/163731416457694), which is a reduction of ~12%.
ghstack-source-id: 134634610
Test Plan: See the AI Bench links above.
Reviewed By: raziel
Differential Revision: D29812191
fbshipit-source-id: 57810fdc1ac515305f5504f88ac5e9e4319e9d28
