MEASURED on a 14,056-noun / 72,679-verb production-shaped store, measured
solo under an exclusive lock: the vfs-bootstrap phase cost 43,021 ms of a cold open and 52,696 ms of
a WARM REOPEN. What dominates it is a migration sweep — a filtered find() over
the whole store hunting for root directories created before the fixed root id
existed. A store either carries such duplicates or never will, and the sweep
ran on every open, forever, in the foreground.
It is now caused by the store's state instead of by the open count: a durable
marker under _system/ records that the sweep has run, and a store carrying it
never sweeps again. A store without one sweeps in the BACKGROUND — the sweep
only removes duplicate roots, nothing serves from them, and it was already
declared non-critical — narrated at both ends, with whenRootSweepSettled() for
anyone who needs to observe rather than race it. An adapter with no raw-object
door keeps the old behaviour: correctness over cost, never a silent skip.
Pins: tests/integration/vfs-root-sweep-once.test.ts — the sweep runs on the
first open and never on the second or third; a sweep slowed to 4s does not
delay the open.
David Snelling
793e9e5787