Jeff Wartes created SOLR-8944:
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Summary: Improve geospatial garbage generation
Key: SOLR-8944
URL: https://issues.apache.org/jira/browse/SOLR-8944
Project: Solr
Issue Type: Improvement
Reporter: Jeff Wartes
I’ve been continuing some analysis into JVM garbage sources in my Solr index.
(5.4, 86M docs/core, 56k 99.9th percentile hit count with my query corpus)
After applying SOLR-8922, I find my biggest source of garbage by a literal
order of magnitude (by size) is the long[] allocated by FixedBitSet. From the
backtraces, it appears the biggest source of FixBitSet creation in my case (by
two orders of magnitude) is my use of queries that involve geospatial filtering.
Specifically, IntersectsPrefixTreeQuery.getDocIdSet, here:
https://github.com/apache/lucene-solr/blob/569b6ca9ca439ee82734622f35f6b6342c0e9228/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/IntersectsPrefixTreeQuery.java#L60
Has this been considered for optimization? I can think of a few paths:
1. Persistent Object pools - FixedBitSet size is allocated based on maxDoc,
which presumably changes less frequently than queries are issued. If an
existing FixedBitSet were not available from a pool, the worst case (create a
new one) would be no worse than the current behavior. The complication would be
enforcement around when to return the object to the pool, but it looks like
this has some lifecycle hooks already.
2. I note that a thing called a SparseFixedBitSet already exists, and puts
considerable effort into allocating smaller chunks only as necessary. Is this
not usable for this purpose? How significant is the performance difference?
I'd be happy to spend some time on a patch, but I was hoping for a little more
data around the current choices before choosing an approach.
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