change default grain size in gather scatter kernel to improve CPU performance (#72082)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/72082
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64478
Test Plan: Imported from OSS
Reviewed By: VitalyFedyunin
Differential Revision: D33862395
Pulled By: frank-wei
fbshipit-source-id: 1e439d90b56294f27aaa7905bc81e772cf47fbbf
(cherry picked from commit 1064561fec2df83b8a20bfd44c205a47af8ef03b)
