[LU-13096] incorrect used_mb in max_cached_mb

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.14.0
• Severity: 3
• Assignee: Emoly Liu
• Reporter: Emoly Liu

Description

it seems to print incorrect used_mb size in max_cached_mb on large memory client.
that client has 24TB memory and it has 12TB for max_cached_mb by default, but max_cached_mb says most of cache is "used_mb".

sdf2{root}1014: free
              total        used        free      shared  buff/cache   available
Mem:    24965051716   139544736 24824112084       39772     1394896 24818988328
Swap:       8388604           0     8388604
sdf2{root}1015: lctl get_param llite.*.max_cached_mb
llite.lustre-ffff96631b3d6800.max_cached_mb=
users: 16
max_cached_mb: 12189966
used_mb: 12157198
unused_mb: 32768
reclaim_count: 0

'Drop cache' doesn't help niether.

sdf2{root}1016: echo 3 > /proc/sys/vm/drop_caches 
sdf2{root}1017: lctl get_param llite.*.max_cached_mb
llite.lustre-ffff96631b3d6800.max_cached_mb=
users: 16
max_cached_mb: 12189966
used_mb: 12157198
unused_mb: 32768
reclaim_count: 0