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Author SHA1 Message Date
0c9b2c45d8 feat(db-bench): measure the RAM ceiling — databasev2 1
- `Wide` text-heavy reference shape beside Int-only `Item`
- `growth N int|text`: per-decile RSS read from own /proc/self/status
- `growth-verify`: survivor of a crash must be a contiguous intact prefix
- four footprint legs under a rootless cgroup v2 cap, swap on/off
- `ceiling` leg: die at the cap, then replay must come back intact
- footprint read as median-of-marginals; doublings a separate metric
- 121 checks, 0 failures; footprint gated ±10%, kill-timing ±100%

Measured, and it inverted two of the iteration's own predictions:

- footprint 96.5-100 B/row Int vs 320.6-324 B/row text = 3.3x, NOT the
  "order of magnitude" three docs asserted
- table storage has NO checked ceiling: SIGKILL signal 9, not a catchable
  WO_T_OOM. overcommit lets malloc succeed; kernel kills on page touch
- swap is NOT latency collapse: 900k rows 148s capped-with-swap vs 150s
  uncapped. Append-mostly never re-touches cold pages
- ack-after-fsync survives an OOM kill: ~40k rows, no holes, no corruption
- iteration 2's budget dependency is REMOVED not satisfied — there is no
  "swap onset" to derive a fraction from

- fix: subprocess returncode -9 was labelled a "checked refusal"; 137 is
  the shell spelling of the same signal

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-27 20:18:47 +02:00
a8829232dc docs: perf-targets register — measured optimization candidates
- target 1: write path (update-through-query re-probe, triple index
  walk, per-field encode, whole-row WAL update record) — re-measure
  after 23, then decide
- targets 2-4 recorded with owners (DB-RPC by design/24, mutex inbox
  /31, fsync bound /23)
- board pending + comparison README link the register

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-08-22 17:19:46 +02:00