[YARN-6680] Avoid locking overhead for NO_LABEL lookups

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.8.0
• Fix Version/s: 2.9.0, 3.0.0-alpha4, 2.8.2
• Component/s: resourcemanager
• Target Version/s: 2.8.2
• Hadoop Flags: Reviewed
• Assignee: Daryn Sharp
• Reporter: Daryn Sharp
• Created: 01/Jun/17 16:37
• Updated: 26/Jun/17 20:22
• Resolved: 19/Jun/17 17:29

Description

Labels are managed via a hash that is protected with a read lock. The lock acquire and release are each just as expensive as the hash lookup itself - resulting in a 3X slowdown.