[C++] Plasma Seal is slow due to hashing

[asfimport]

When I writes a 1MB tensor into plasma, it takes about 2ms. 50% of time is spent sealing the object. Can we add a flag to the Seal API to disable to hashing when needed?

 

For example:

 Status PlasmaClient::Seal(const ObjectID& object_id, bool hash_flag)

 

cc @pcmoritz

Reporter: Simon Mo / @simon-mo

_{Note: This issue was originally created as ARROW-2916. Please see the migration documentation for further details.}

[asfimport]

Robert Nishihara / @robertnishihara:
In my experience, profilers often show the hashing taking up a bunch of time, but when I actually comment out the hashing, things don't get faster.