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Keyword cache cleanup incurs linear scan of cache

Description

If the GC reclaims a keyword, any subsequent attempt to create a keyword requires an O(n) scan over the entire keyword table via Util.clearCache. This is a significant performance cost in keyword-heavy operations; e.g. JSON parsing.

Patch: keyword-cache.diff - patch to defer cleaning till portion of the table is dead and avoid multiple threads cleaning simultaneously.

Patch: kw-clean-future.patch - patch to spin cache cleaning into a future. Found that 1) this introduces some ordering constraints and circularity between Agent and Keyword (fixable) and 2) using the future pool for this means shutdown-agents would always need to be called (in the patch I avoided this by changing agent's soloExecutor to use daemon threads.

Patch: unified-kw-patch.diff - Alternative to keyword-cache and clean-future.patch. Combines all keyword-perf changes, including the EDN kw parser improvement, improved table lookup performance, and has threads cooperate to empty the table refqueue with a minimum of contention.

Environment

None

Status

Assignee

Alex Miller

Reporter

Kyle Kingsbury

Approval

Vetted

Patch

Code

Fix versions

Affects versions

Release 1.6

Priority

Minor