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From "Simon Willnauer (JIRA)" <>
Subject [jira] [Commented] (LUCENE-8757) Better Segment To Thread Mapping Algorithm
Date Tue, 07 May 2019 08:55:00 GMT


Simon Willnauer commented on LUCENE-8757:

[~atris] actually I thought about these defaults again and I am starting to think it's an
ok default. The reason for this is that we try to prevent having dedicated threads for smallish
segments so we group them together. I still do wonder if we need to have 2 parameters? Wouldn't
it be enough to just say that we group things together until we have at least 250k docs per
thread to be searched? is it really necessary to have another parameter that limits the number
of segmetns per slice? I think a single parameter would be great and simpler. WDYT?

> Better Segment To Thread Mapping Algorithm
> ------------------------------------------
>                 Key: LUCENE-8757
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Atri Sharma
>            Priority: Major
>         Attachments: LUCENE-8757.patch
> The current segments to threads allocation algorithm always allocates one thread per
segment. This is detrimental to performance in case of skew in segment sizes since small segments
also get their dedicated thread. This can lead to performance degradation due to context switching
> A better algorithm which is cognizant of size skew would have better performance for
realistic scenarios

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