[HARMONY-6362] Logging performance improvements

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 5.0M12
• Component/s: Classlib
• Environment: SVN Revision: 829932
• Patch Info: Patch Available
• Estimated Complexity: Moderate
• Assignee: Unassigned
• Reporter: Jesse Wilson
• Created: 26/Oct/09 20:32
• Updated: 09/Nov/09 12:25
• Resolved: 06/Nov/09 18:02

Description

The logging module performs more synchronization and object allocation than necessary. In particular, getHandlers() always needs synchronization and creates an array. By adopting util.concurrent features (CopyOnWriteArrayList) and coding to the common case (when there are zero handlers) I saw a 2.5x improvement in throughput for calls to logger.log(Level, String). In a benchmark that measures calls to "logger.info", call time improved from 385000ns to 154000ns per message.

Here's an overview of the patch:

• Reduce the use of synchronization by adopting a CopyOnWriteArrayList for Handlers
• Reduce object creation by reusing a 0-length handlers array in getHandlers()
• Load handlers on logger creation rather than on receipt of the first message. This also fixes a behavioural inconsistency with the RI. I've got a test case that demonstrates this.
• Cleanup synchronization by moving methods with "synchronized (LogManager.getManager())" blocks to the LogManager class

I've got the patch ready to submit upstream. I'll submit it when my commit privileges are granted, unless anyone raises objections here.