Support Faiss parallel_mode parameter

[weiwang19]

When evaluate Faiss performance we see that if the parallel mode is changed ( parallel_mode=2) we can get better performance on single vector queries, one example:

  parallel mode             Index                    num_threads           Leaves searched          single vector query latency 
       0 (default)   |   IVF8192,PQ128  |          56                  |       16                        |        27.6
             2             |   IVF8192,PQ128  |          56                  |       16                        |        11.3 

Not much difference is observed with 1000 batch vectors. Can Milvus expose the parallel_mode parameter to be configurable?

[cydrain]

/assign

[cydrain]

Hi @weiwang19, this is a good suggestion, we will evaluate and see if this can be done in the next release.

[weiwang19]

Hi is there plan to have the change in recent release?