Thread

Missing wait events (gap analysis)

Nikolay Samokhvalov <nik@postgres.ai> — 2025-11-22T00:43:31Z

Hi hi

Many tools that implement wait event analysis, when visualizing samples
with "wait_event is null" use green color and "CPU" (perhaps, it started
with RDS Performance Insights and PASH Viewer and, I suppose, originally
came from the Oracle world, and now I see it in many more places).

I don't have any concerns with green color, but always had a feeling that
"coalesce(wait_event, 'CPU')" is an assumption that can make analysis
inaccurate, because there may be a lot of places in the code that are not
covered by wait events, but technically should -- and such places cannot be
named "CPU".

I asked Claude Code to analyze Postgres source code and find such places,
that we could potentially cover with more wait events. Here is the first
result:
https://github.com/NikolayS/postgres/blob/claude/cpu-asterisk-wait-events-01CyiYYMMcFMovuqPqLNcp8T/WAIT_EVENTS_ANALYSIS.md

Before moving forward with proposals of specific patches, I wanted to hear
opinions -- does it make sense to work in this direction?

Nik