[LU-13563] WBC: Reclaim mechanism for cached inodes and pages under limits in MemFS

• Type: Technical task
• Resolution: Unresolved
• Priority: Minor
• Assignee: Qian Yingjin
• Reporter: Qian Yingjin

Description

It would better to design a reclaim mechanism to free up some reserved inodes for newly creation or cache pages for latter I/O in case of cache saturation.
We could use a kernel shrinker daemon that runs periodically:

• Unreserve inodes cached in MemFS.
• Commit the cache pages from MemFS into Lustre (assimilation phase) and unaccount all cached pages from the MemFS limits.

The cache shrinker starts to work if the cache allocation has become larger than the upper watermark and it evicts files until the allocation is below a lower watermark.