gc before warming up benchmarking (#159670)
Summary:
#158649 turned off automatic GCs during cudagraph recording. This is causing a small uptick in some internal benchmark numbers because of memory the benchmark is leaving around before the benchmark starts - so GC before warming up the model.
X-link: https://github.com/pytorch/pytorch/pull/159670
Approved by: https://github.com/oulgen
Reviewed By: izaitsevfb, yangw-dev
Differential Revision: D79534767
fbshipit-source-id: 2eee7562810be2082e7d11cb4104557903a8e1a8
