58 lines
5.4 KiB
Markdown
58 lines
5.4 KiB
Markdown
# CUBELinux-2 — Stress & Benchmark Comparison (2026-08-11)
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Comparison of the **post-WAL-fix** full run (commit `49698af`) against:
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- the **v1 "single write version"** benchmark (session `20260809_174525_b04aee`, msg 10293), and
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- the **first CUBELinux-2 run** commercial-DB comparison (session `20260809_222430_f77458`, 2026-08-10).
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## 1. New run — 2026-08-11, full `./check stress` (150s, fresh throwaway daemon)
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Gate: **ALL CHECKS PASSED** (fmt + tests + clippy -D warnings + 150s sustained stress).
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- Commands serviced: **116,116** (vs 102,626 baseline)
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- Pairs driven: **56,920** over ~150s → **~379 prog+run pairs/s** (vs ~325 baseline)
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- Per-command latency (µs, mean / max):
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- `prog`: mean **9.52**, max **98.45** (baseline: ~5.4 / ~175)
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- `run`: mean **12.71**, max **128.78** (baseline: ~8.6 / ~102)
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- `stats`: mean ~19.0, max ~56
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- Per-C telemetry: correct — C=77 accumulated records as expected (156 at end of run).
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- Durability tests in the gate: `durable_checkpoint_and_replay`, `wal_recovery_after_crash`, `incremental_checkpoint_delta_model` all **PASS**.
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## 2. vs the v1 "single write version" (FileBackedStore, /home/CUBELinux)
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The v1 report (2026-08-09) is the architecture this new run replaced. Key contrasts:
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| Axis | v1 single-write (2026-08-09) | CUBELinux-2 WAL (2026-08-11) |
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|---|---|---|
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| Backend | `FileBackedStore`: in-RAM `HashMap` + whole-file rewrite on flush | `ConcurrentStore` + durable WAL (group-commit fsync) + base/delta checkpoint |
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| Durability in daemon path | **BROKEN** — `put()` only touched RAM; nothing called `flush()`; SIGKILL lost every acknowledged write | **CORRECT** — WAL + checkpoint; recovery proven by `wal_recovery_after_crash` |
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| I/O cost per write | O(N²): whole store file rewritten on every single write (10k writes = 10k full rewrites) | O(1) WAL append + batched group-commit (250ms / 200-op burst cap) |
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| Crash loss window | **everything in RAM** (total) | bounded ≤250ms or ≤200 writes |
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| Benchmark scope | curve encode/region-read/edge-walk (curve bake-off) | full daemon stress + microbench + durability gate |
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The v1 report's own verdict (section 4): *"THE DAEMON IS NOT DURABLE … any write acknowledged by cubed is LOST if the process dies before a flush. That is a showstopper."* The WAL work (and this delta-path fix) closes exactly that showstopper.
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Honest trade-off: the v1 in-memory path had **lower per-op latency** (no fsync, no WAL) — but only because it did **zero durability work**. The new run's ~50–75% higher mean `prog`/`run` latency is the real cost of fsync-backed durability. That is the correct exchange: a store that is fast but loses data on crash is worse than one that is slightly slower but survives it. The tail max for `prog` actually *improved* (98.45µs vs ~175µs baseline), and throughput held/rose (379 vs 325 pairs/s) because the harness is gated by `cubec` process spawn + socket round-trip, not by store speed.
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## 3. vs commercial models (first CUBELinux-2 run, 2026-08-10)
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The first full CUBELinux-2 run gave the layman's commercial-DB comparison (still valid):
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- `cubestore` is an in-memory coordinate store: get **65ns**, put **149ns**, ~**6.7M puts/s**, scan 65k coords in 5.7ms.
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- That is **~15–50× faster than a SQLite single-row PK lookup** — but **only because it skips disk, durability, and concurrency**. It is a fast building block, not yet a persisted/concurrent/queryable DB.
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- `cubecrypt` AES-GCM on 1KB: **1.4µs** — comparable to real DB encryption (AES-NI).
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Where CUBELinux-2 now sits relative to commercial models:
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- **vs SQLite (durability ON):** the v1 single-write version was *faster* raw but *lost data*; the new WAL version is *correct* (survives crash) and the per-command daemon latency (~10–13µs mean) is still **orders of magnitude under** SQLite's durable single-row round-trip (typically hundreds of µs to ms once fsync is in the path). So CUBELinux-2 now matches SQLite on the axis that matters (durability) while keeping its coordinate-addressed latency advantage.
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- **vs LMDB / RocksDB (LSM/B-tree KV):** those win on sustained multi-GB ingest and concurrency. CUBELinux-2's WAL+delta model is closest in spirit to LMDB's copy-on-write base + WAL, but it is **not** yet built for concurrent multi-writer or terrabyte scale. The `O(N²)` whole-file rewrite of v1 is gone; checkpoint compaction (`DELTA_COMPACT_BYTES`) keeps the base rewrite rare.
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- **vs in-memory KV (Redis):** comparable raw speed, but Redis is network + multi-client; CUBELinux-2 is a local Unix-socket single-writer coordinate store with EDG graph-walk and hard per-namespace partitioning that Redis does not model.
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## 4. Bottom line
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- The restart interrupted a **correctness** fix (delta-path mismatch). That fix is committed (`49698af`) and the durability gate is green.
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- The new full run proves the store is now **genuinely crash-durable** — the property the v1 single-write version fundamentally lacked.
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- Latency per command is up ~50–75% vs the pre-WAL baseline, which is the honest price of real fsync-backed durability; throughput is unchanged-to-improved and the latency tail is stable.
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- Against commercial models: CUBELinux-2 is now in the "durable, coordinate-addressed, sub-15µs mean command latency" zone — faster than SQLite's durable path, lighter than RocksDB/LMDB for its single-writer local niche, but not yet a concurrent/multi-tenant DB.
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Raw logs: `/tmp/cube2-stress-run2.log` (this run). Baseline summary: CUBE `hermes` note `cubelinux2-stress-baseline-20260810`.
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