[HADOOP-6133] ReflectionUtils performance regression

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.20.0
• Fix Version/s: 0.21.0
• Component/s: conf
• Hadoop Flags: Reviewed
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 08/Jul/09 22:06
• Updated: 30/Jul/12 14:37
• Resolved: 07/Sep/09 21:55

Description

HADOOP-4187 introduced extra calls to Class.forName in ReflectionUtils.setConf. This caused a fairly large performance regression. Attached is a microbenchmark that shows the following timings (ms) for 100M constructions of new instances:

Explicit construction (new Test): around ~1.6sec
Using Test.class.newInstance: around ~2.6sec
ReflectionUtils on 0.18.3: ~8.0sec
ReflectionUtils on 0.20.0: ~200sec

This illustrates the ~80x slowdown caused by HADOOP-4187.

Issue Links

• breaks: HADOOP-8632 Configuration leaking class-loaders