Adjust Gc control parameters to use best-fit allocator with overhead 120
Adjust Gc control parameters to use best-fit allocator with overhead 120

Summary:
The best-fit allocator with overhead 120 is slightly faster, and
significantly reduces peak memory usages in the workers.

Reviewed By: jvillard

Differential Revision: D23678794

fbshipit-source-id: ccdfced74

jvillard/infer,jvillard/infer,jvillard/infer,facebook/infer,facebook/infer,jvillard/infer,facebook/infer,facebook/infer,facebook/infer,jvillard/infer,facebook/infer,jvillard/infer,facebook/infer,jvillard/infer