[LU-13365] spin_lock in after_reply() eat up most of cpu

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.14.0
• Affects Version/s: Lustre 2.14.0
• Environment: master
• Severity: 3
• Assignee: Wang Shilong (Inactive)
• Reporter: Shuichi Ihara

Description

There are two clients, but one of client was 25% slower write than other client. According to an framegraph on CPU time of each client, client spent amount of CPU time with spin_lock at after_reply(). However, fast client didn't show that cpu time on after_reply().
The workload is simple 1MB, FPP with IOR. (mpirun -np 16 ior -t 1m -b 16g -e -F -vv -o /fast/file -w)
Here is two client's node information and performance results.

fast client (2 x Platinum 8160 CPU, 192GB memory, 1 x IB-EDR)
Max Write: 11219.97 MiB/sec (11765.00 MB/sec)
slow client (1 x Gold 5218 CPU, 96GB memory, 1 x IB-HDR100)
Max Write: 9278.14 MiB/sec (9728.84 MB/sec)