[IMPALA-3342] Runtime profile TotalCpuTime are often wrong

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: impala 2.3
• Fix Version/s: Impala 2.8.0
• Component/s: Backend
• Target Version: Product Backlog
• Assignee: Anuj Phadke
• Reporter: Juan Yu
• Created: 13/Apr/16 16:26
• Updated: 29/Nov/16 10:29
• Resolved: 29/Nov/16 10:29

Description

When tracking scanner thread CPU time, Impala simply uses the wall clock time from thread start to finish. it doesn't eliminate the waiting time. so the TotalCpuTime is much higher than scanner actually use.
The plan fragment execution CPU time might have similar issue. although it does eliminate disk IO and network transmit time, it might include waiting time for downstream fragments.