[LUCENE-3648] Speed up SegementDocsEnum by making it more friendly for JIT optimizations

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0-ALPHA
• Fix Version/s: 4.0-ALPHA
• Component/s: core/codecs, core/search
• Lucene Fields: New, Patch Available
• Assignee: Simon Willnauer
• Reporter: Simon Willnauer
• Created: 14/Dec/11 14:06
• Updated: 28/Aug/22 13:03
• Resolved: 16/Dec/11 08:43

Description

Since we moved the bulk reading into the codec ie. make all bulk reading codec private in LUCENE-3584 we have seen some performance regression on different CPUs. I tried to optimize the implementation to make it more eligible for runtime optimizations, tried to make loops JIT friendly by moving out branches where I can, minimize member access in all loops, use final members where possible and specialize the two common cases With & Without LiveDocs.

I will attache a patch and my benchmark results in a minute.