[LU-12651] High kworker CPU usage (osc_grant_work_handler) on IDLE connections

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.14.0, Lustre 2.12.5
• Affects Version/s: Lustre 2.12.2
• Labels: LTS12
• Severity: 3
• Assignee: Alexander Zarochentsev
• Reporter: Jacek Tomaka (Inactive)

Description

We discovered that on our systems with lustre mounted, the kworker is using signifficant amount of CPU.
perf top shows on an idle system:

 39.44%  [kernel]                  [k] osc_should_shrink_grant
  12.14%  [kernel]                  [k] osc_grant_work_handler
   2.81%  [kernel]                  [k] process_one_work
   2.64%  [kernel]                  [k] __queue_work
   2.56%  [kernel]                  [k] read_tsc

We currently have grant_shrink=0 on this system.

Looks like doing just du -hs /fs makes the problem go away for some time.
Also unmounting the filesystem makes the problem go away.
This is Centos 7.6 system with Lustre 2.12.0

Issue Links

• is related to: LU-8708 Grant shrinking disabled all the time