[LU-18166] PCC: Adding sub command in pcc to cleanup FID directories

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Severity: 3
• Assignee: Qian Yingjin
• Reporter: Qian Yingjin

Description

The customer is using PCC on their large HPC cluster in production.
They asked how cleanup unnecessary DIRs for FIDs in PCC.

# systemctl restart lpcc
# lctl get_param llite.*.pcc
llite.exafs-ff27030794ba9000.pcc=
pcc:
  -
    pccpath: /pcc
    hsmtool: posix_v2
    rwid: 0
    roid: 3
    flags: ae
    autocache: projid={500}
# mkdir /exafs/projid500/
# lfs project -srp 500 /exafs/projid500/
# dd if=/exafs/projid500/miniconda3/bin/bunzip2 of=/dev/null
# ls -l /pcc/2064/0x4c0000bd1\:0x2bb5\:0x0 

"lctl pcc" clear pcc, but it removes everything include pcc configuration

# lctl pcc clear /exafs/
# lctl get_param llite.*.pcc
#

# find /pcc/
/pcc/
/pcc/2064

But, still DIR "2064" is not cleaned up.

They would add an option to cleanup those DIRs if it's unnecessary.
A related thing, 'lctl pcc clear' is not good idea since it deletes PCC everything includes configurations.
I think that it would be nice to add an option to 'lctl pcc clear' to cleanup only PCC caches and stay pcc configurations.