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https://issues.apache.org/jira/browse/LUCENE-2840?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12976027#action_12976027
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Earwin Burrfoot commented on LUCENE-2840:
-----------------------------------------

I use the following scheme:
* There is a fixed pool of threads shared by all searches, that limits total 
concurrency.
* Each new search apprehends at most a fixed number of threads from this pool 
(say, 2-3 of 8 in my setup),
* and these threads churn through segments as through a queue (in maxDoc order, 
but I think even that is unnecessary).

No special smart binding between threads and segments (eg. 1 thread for each 
biggie, 1 thread for all of the small ones) -
means simpler code, and zero possibility of stalling, when there are threads to 
run, segments to search, but binding policy does not connect them.
Using fewer threads per-search than total available is a precaution against 
biggie searches blocking fast ones.

> Multi-Threading in IndexSearcher (after removal of MultiSearcher and 
> ParallelMultiSearcher)
> -------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-2840
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2840
>             Project: Lucene - Java
>          Issue Type: Sub-task
>          Components: Search
>            Reporter: Uwe Schindler
>            Priority: Minor
>             Fix For: 4.0
>
>
> Spin-off from parent issue:
> {quote}
> We should discuss about how many threads should be spawned. If you have an 
> index with many segments, even small ones, I think only the larger segments 
> should be separate threads, all others should be handled sequentially. So 
> maybe add a maxThreads cound, then sort the IndexReaders by maxDoc and then 
> only spawn maxThreads-1 threads for the bigger readers and then one 
> additional thread for the rest?
> {quote}

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