[LU-17872] do not check reclaim full for every lock request

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.16.0
• Severity: 3
• Assignee: Patrick Farrell (Inactive)
• Reporter: Patrick Farrell (Inactive)

Description

Checking reclaim full for every lock request is expensive - it require taking a global spinlock and takes up 10% of MDS CPU time under load, but is not necessary to do this check for every single lock request - it is OK if we very slightly exceed the reclaim limit. Instead, check it once for every 100 requests.  100 is chosen arbitrarily but should be sufficient for good performance.