add options to flush cache in SLS benchmarks (#25530)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25530
Add an option to flush cache for more consistent benchmarking.
Test Plan:
buck run mode/opt caffe2/caffe2/fb/python/benchmarks:sparse_lengths_sum_4bit_benchmark -- --flush-cache
buck run mode/opt caffe2/caffe2/python/operator_test:sparse_lengths_sum_benchmark -- --flush-cache
Reviewed By: hyuen
Differential Revision: D17148087
fbshipit-source-id: 7eb782986676620254c1619a9a48c656cb1a6856
