[SOLR-8922] DocSetCollector can allocate massive garbage on large indexes

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Assignee: Yonik Seeley
• Reporter: Jeff Wartes
• Created: 30/Mar/16 21:34
• Updated: 20/Apr/16 12:40
• Resolved: 09/Apr/16 23:11

Description

After reaching a point of diminishing returns tuning the GC collector, I decided to take a look at where the garbage was coming from. To my surprise, it turned out that for my index and query set, almost 60% of the garbage was coming from this single line:

https://github.com/apache/lucene-solr/blob/94c04237cce44cac1e40e1b8b6ee6a6addc001a5/solr/core/src/java/org/apache/solr/search/DocSetCollector.java#L49

This is due to the simple fact that I have 86M documents in my shards. Allocating a scratch array big enough to track a result set 1/64th of my index (1.3M) is also almost certainly excessive, considering my 99.9th percentile hit count is less than 56k.

Issue Links

• relates to: SOLR-5444 Slow response on facet search, lots of facets, asking for few facets in response