shoney.arickathil
3a30b4ac3b
- bench/baseline.json: 74 metrics from the first full campaign; tolerances tuned by a two-run repeatability check (mix* 50%, read/query 35%, rest 15% — rationale in _config) - gate bites: --check mode; doctored copy fails, both real runs 74/0 - headline: durable seed 4.5k/s vs ram 297k/s (23's case); reads O(table) at ~1.5k/s; mixread 1280 vs 21 ops/s single-vs-multi (the arc's price); msgrate 13.4M vs 2.45M (mutex-inbox number) - arc delta recorded in story 8; findings in sample README Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
63 lines
3.4 KiB
Markdown
63 lines
3.4 KiB
Markdown
# db-bench — iteration 22's load generator
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The measurement backbone (spec:
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`docs/superpowers/specs/2026-08-21-db-bench-design.md`). Pure `.wo`;
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every measured mode prints one machine-parsable line per operation
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class:
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<op> <count> <ops/sec> <p50us> <p99us>
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Timing is per-operation via `time.ticks` (CLOCK_MONOTONIC µs).
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Percentiles come from a 1µs-bucket histogram clamped at 20000µs — exact
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to the microsecond below the clamp; a p99 AT 20000 means "clamp or
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worse". (A histogram, not the spec's reservoir: the language has no
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container element-write or sort, and the histogram's tail fidelity is
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strictly better. Recorded as a plan deviation.)
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## Modes
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| mode | what it prices |
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| --- | --- |
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| `all N` | the throughput campaign in ONE process: seed N, read N/2, query N/10, write N/2. Without `WO_DATA` the store is RAM and dies with the process, so the measured modes must share the seeding run. |
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| `seed N` | timed inserts: one parent per 100 children (FK probe each insert, unique-index maintenance per parent), k non-unique (10 rows/key), deterministic v. Writes `Meta` expectation rows. |
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| `read N` | indexed take-1 point lookups, LCG-spread keys. |
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| `query N` | full equality probes on the k index (≈10 rows each), materialized and counted. |
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| `write N` | alternating inserts (disjoint k range 2e6+) and updates through query results. Corrupts the checksum by design — durability legs run on a fresh store. |
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| `wal N` | the crash battery's vehicle: insert-only (k range 1e6+), `acked <i>` printed AFTER each insert returns — the return IS the ack (RAM applied, WAL record staged, ONE commit done). |
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| `verify` | store vs its own Meta rows: count, checksum, one unique probe. Exit 3 on mismatch. |
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| `verify-acked M` | after kill -9 mid-`wal`: rows 1..M exist with the right v; rows beyond M allowed (acked after the last print flushed). Exit 3 on mismatch. |
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## Coordination idiom (this side of iteration 31)
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There is no request/response surface yet: concurrent modes drive
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completion the db-actor way — actors write rows, main polls the store
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until the expected count, then settles. Retired when 31 lands.
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## Standing finding (2026-08-21, first run)
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A hand-built `multi Bucket` of insert results SEGVs on drop: the
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compiler classifies the elements OWNED while table refs are scalar ids.
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Query-built multis are runtime-typed and safe. Worked around here
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(single ref local, bucket-major seeding); the compiler fix is its own
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slice.
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## Reference-machine numbers (first campaign, 2026-08-21)
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`bench/baseline.json` is the contract; headline readings:
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- ram seed 257–298k inserts/s; **durable seed ≈4.5k/s** (fsync-per-commit
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≈220µs each — the gap iteration 23 exists to close).
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- reads ≈1.5k/s at p50 ≈600µs on a 20k-row store: point lookups are
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O(table) — the probe walks every slab; index selection never reaches
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the lookup path. THE read-path finding.
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- mixread 1,280 ops/s single-shard vs **21 ops/s** multi-shard: RPC
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round-trip × O(table) probes × owner serialization — the arc's honest
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price until reads index properly.
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- msgrate 13.4M msgs/s same-heap vs 2.45M cross-shard (the mutex-inbox
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number, stage-2 deviation 4).
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## The gate must bite (proven 2026-08-21)
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`scripts/db-bench.py --check <results.json>` evaluates a recorded run:
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the real results pass 74/0; a doctored copy (one ops/sec halved) FAILS
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on exactly that metric. Re-run the smoke after any gate change.
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