[LU-6676] Excessive blocking ast RPC for LDLM locks in waiting list

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Severity: 3
• Assignee: WC Triage
• Reporter: Jinshan Xiong (Inactive)

Description

In current implementation of LDLM lock, if a lock is in waiting list and blocks a newly enqueued lock, the waiting lock will be added into work_list and blocking AST will be sent against this lock.

This is a waste of effort because the lock is not granted yet, usually the client holds a reader/writer counter so blocking AST can't do anything to the lock;

Actually the server doesn't need to send the blocking AST RPC for waiting locks, instead it can just set LDLM_FL_AST_SENT flag and this flag will be piggied back by completion AST later.