[LU-9221] Create pid-based hash to enhance Jobstats performance

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.11.0
• Affects Version/s: Lustre 2.9.0

Epic/Theme

Performance

• Assignee: Ben Evans (Inactive)
• Reporter: Ben Evans (Inactive)

Description

Currently jobstats gets information by either dedicating an entire node to a single job (LU-7195) or reading from the userspace environment for each call. The first is very fast, but can be inaccurate, the second introduces a significant performance penalty on the client. This patch creates a cache of JobID names mapped to PIDs. It has several fallback mechanisms in order to present the most accurate info available.

Issue Links

• is related to: LUDOC-381 Improve documentation for jobstats
• links to: https://review.whamcloud.com/#/c/25208/