[LU-17197] Performance regression with "LU-15947 obdclass: improve precision of wakeups for mod_rpcs"

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.16.0, Lustre 2.15.5
• Severity: 3
• Assignee: Shaun Tancheff
• Reporter: Shaun Tancheff

Description

A performance regression:

Introduced MDTest Unique Directory Directory (-25%)/File Removal(-11%)/File Reads Regressions

mdtest -v -i 5 -p 120 -C -w 32768 -E -e 32768 -T -r -n 3120 -u -d <dir>
...
mdtest -v -i 5 -p 120 -C -E -T -r -n 3120 -u -d  <dir>

Also an IOR 4k sequential read (-6%)

ior -F -r -t 4k -D 180 -u -b 8g -o <path>
...
Options: 
api                 : POSIX
apiVersion          : 
test filename       : /mnt/kjlmo2/pkoutoupis/flash/test.05
access              : file-per-process
type                : independent
segments            : 1
ordering in a file  : sequential
ordering inter file : no tasks offsets
nodes               : 21
tasks               : 336
clients per node    : 16
repetitions         : 1
xfersize            : 4096 bytes
blocksize           : 8 GiB
aggregate filesize  : 2.62 TiB
stonewallingTime    : 180
stoneWallingWearOut : 0

Issue Links

• is related to: LU-17938 Client evicted during stress test
• is related to: LU-17510 Client hung on ll_file_open
• is related to: LU-15947 Spinlock contention during wake_up_all() in obd_put_mod_rpc_slot()