[YARN-5969] FairShareComparator: Cache value of getResourceUsage for better performance

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.7.1
• Fix Version/s: 2.9.0, 3.0.0-alpha2
• Component/s: fairscheduler
• Hadoop Flags: Reviewed
• Assignee: zhangshilong
• Reporter: zhangshilong
• Created: 06/Dec/16 03:49
• Updated: 28/Dec/16 18:03
• Resolved: 27/Dec/16 20:36

Description

in FairShareComparator class, the performance of function getResourceUsage() is very poor. It will be executed above 100,000,000 times per second.
In our scene, It takes 20 seconds per minute.
A simple solution is to reduce call counts of the function.