Does Sphinx realtime index, support multi-threaded search, yet? What if they are part of a distributed index?

Question

Question is related to sphinx real time(rt) indexes. I have a distributed index that contains three rt indexes. Each rt index has about 21 million docs per rt index (total 3 * 21 = 63 million).

I am trying to improve performance of this index configuration, and came across this informative post:

As of this moment, the RT index will use only one core per search, no matter how many disk chunks it has (this may change in the future!).

Source http://sphinxsearch.com/blog/2014/02/12/rt_performance_basics/comment-page-1/ (Link dated 2014)

Does the above statement mean that the above configuration for the indexes will always run in a single threaded manner per search, so if I have three rt indexes in a distributed index, on a four core machine, only three searches can be done simultaneously, which will then be distributed on three cores by the distributed index?

sphinx fulltext indexing

Answer 1

The distributed index should run each component index in a new thread, but each RT index will be singled threaded.

... so it could use 3 cores to run the query (one RT index per core)

But, note the mapping of threads to cores is NOT absolute. That's up to the OS. The three 'threads' could end up being run on one core. ... also sphinx isnt restricted to just running as many threads as there are cores. It may spawn more threads, which compete for cores.