a71e467381
Summary: Enable readahead for blob DB garbage collection, which should improve GC performance a little bit. Closes https://github.com/facebook/rocksdb/pull/3648 Differential Revision: D7383791 Pulled By: yiwu-arbug fbshipit-source-id: 642b3327f7105eca85986d3fb2d8f960a3d83cf1