Clean up tracing feature?

Investigate tracing feature (remove it if no perf impact) on the host

Begin by locating the host-side tracing feature and its callers; the issue names no files or tests. Compare host behavior and performance with tracing enabled and removed, then use relevant existing tests or benchmarks if available. Done means establishing whether tracing can be removed without performance impact and making the resulting cleanup clear.

索引モデルが issue の本文から書いたものです。