[YARN-7397] Reduce lock contention in FairScheduler#getAppWeight()

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1.0
• Fix Version/s: 3.0.0, 3.1.0
• Component/s: fairscheduler
• Target Version/s: 3.1.0
• Hadoop Flags: Reviewed
• Assignee: Daniel Templeton
• Reporter: Daniel Templeton
• Created: 25/Oct/17 23:42
• Updated: 14/Nov/17 06:45
• Resolved: 28/Oct/17 16:19

Description

In profiling the fair scheduler, a large amount of time is spent waiting to get the lock in FairScheduler.getAppWeight(), when the lock isn't actually needed. This patch reduces the scope of the lock to eliminate that contention.