Summary:
The blob cache enables an optimization on the read path: when a blob is found in the cache, we can avoid copying it into the buffer provided by the application. Instead, we can simply transfer ownership of the cache handle to the target `PinnableSlice`. (Note: this relies on the `Cleanable` interface, which is implemented by `PinnableSlice`.)
This has the potential to save a lot of CPU, especially with large blob values.
This task is a part of https://github.com/facebook/rocksdb/issues/10156
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10297
Reviewed By: riversand963
Differential Revision: D37640311
Pulled By: gangliao
fbshipit-source-id: 92de0e35cc703d06c87c5c1861cc2899ec52234a
