The memo held one entry per picture ever rendered, for the life of the process.
Correct for one author's laptop, wrong for what this engine is meant to be: a
server that runs for months and serves a whole site to many readers.
Least-recently-used rather than clearing when full, because a site has pages
nobody opens for months and a front page opened every minute — discarding
wholesale throws away exactly the entries about to be asked for again. A map
into a recency-ordered list: reads promote, evictions take the back, both
constant time.
1024 entries is a few hundred kilobytes. Generous enough that a normal site
never evicts, bounded enough that no site can grow the process without limit.
The number is a constant and not a setting, because a knob with one user is a
knob nobody asked for.
Eviction, replacement and the bound are tested, including under -race, since
requests are concurrent and the store is shared.
Latent item cleared. ext 1975/2000.
Claude Opus 5andbdeshi
6447a995d1