[LUCENE-7115] Speed up FieldCache.CacheEntry toString by setting initial StringBuilder capacity

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: trunk, 6.1
• Component/s: core/search
• Lucene Fields: New
• Assignee: Gregory Chanan
• Reporter: Gregory Chanan
• Created: 18/Mar/16 00:48
• Updated: 28/Aug/22 14:52
• Resolved: 21/Mar/16 18:55

Description

Solr can end up printing a lot of these objects via the JmxMonitoriedMap, see SOLR-8869 and SOLR-6747 as examples.

From looking at some profiles, a lot of time and memory are spent resizing the StringBuilder, which doesn't set the initial capacity.

On my cluster, the strings are a bit over 200 chars; I set the initial capacity to 250 and ran tests calling toString 1000 times. Tests consistently show 10-15% improvement when setting the initial capacity.