Server: TCP_NODELAY on every connection

kayg commented

2026-10-14 07:27:58 +00:00

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Replaces #117: rebased onto dev at 2a2478c (after #112, #123, #130 and the rest), since the forge ignores pushes to an open PR.

Part of #44. Stacked on #180; the diff here is one commit on top.

A reply the server writes in pieces (a room's joined, then the note's state) waited for the client's delayed ACK, about 40 ms, so opening any note took at least that long. The harness showed a flat ~51 ms open.note at every Home size with almost no noise. Every accepted connection now sets TCP_NODELAY (axum tap_io).

Budget: open.note p95 <= 50 ms. Perf VM before/after numbers will follow as a comment.

🤖 Generated with Claude Code

Replaces #117: rebased onto `dev` at 2a2478c (after #112, #123, #130 and the rest), since the forge ignores pushes to an open PR. Part of #44. Stacked on #180; the diff here is one commit on top. A reply the server writes in pieces (a room's `joined`, then the note's state) waited for the client's delayed ACK, about 40 ms, so opening any note took at least that long. The harness showed a flat ~51 ms `open.note` at every Home size with almost no noise. Every accepted connection now sets `TCP_NODELAY` (axum `tap_io`). Budget: `open.note` p95 <= 50 ms. Perf VM before/after numbers will follow as a comment. 🤖 Generated with [Claude Code](https://claude.com/claude-code)

kayg added 8 commits

2026-10-14 07:27:59 +00:00

Perf harness: fixture Homes, server scenarios, budgets 9c57eff20a

`calternal-fixtures` makes realistic Homes (1k/10k/100k notes) in the real
on-disk format, byte-identical for a seed: daily notes with log entries,
regular notes with frontmatter (+05:30 times), links `[t](<path.md>)`,
tags, tasks, attachment refs, 1 in 2,000 notes at 50,000 words, some in a
subfolder, some without a `calternal-id`.

`calternal-perf` runs the real server binary on them: first-start indexing
(cold), then fresh servers on the indexed Home measuring startup to
/healthz, notes.list, journal catch-up, opening notes (room join and
notes.get), sync round trip and save ack, and an edit storm (4 clients,
10k keystrokes with save checks, plus an outside app rewriting the file)
that checks nothing was lost or doubled. RSS and disk bytes written come
from /proc. Median of runs per p50/p95 with a noise figure; budgets in
perf/budgets.json, --gate exits 1 on a breach.

perf/run-vm.sh runs it on the perf machine; perf/browser.sh wraps the
existing @perf keystroke-to-paint browser test.

Part of #44

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Yyy8fQGxPLkLa8v8NXz7T

Perf storm: typing never glues onto an outside line 7aa1d0c836

The storm kept typing before the first "\nOutside line", but a keystroke
right after that newline glued onto the outside line, moved the boundary
past it, and later keystrokes edited it. The check then reported the line
missing, though the server had kept every line exactly once (verified in
the saved files). Typing now stops before the newline ahead of the first
outside line. run-vm.sh copies with tar (no rsync needed) and keeps the
build outside the copied tree.

Part of #44

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Yyy8fQGxPLkLa8v8NXz7T

Perf budgets: one page, baseline from the perf VM 9247e596d4

docs/perf/budgets.md says what each metric measures, how (perf VM, no host
cache, page cache dropped, median of 5 runs, noise), the gated budget and
the target for each, the first baseline at 1k/10k/100k notes, and the
problems it shows: a fake outside change journaled per unopened note on
every start, slow first-start indexing, one fsync per keystroke per room,
and heavy whole-Home lists at 100k. perf/budgets.json holds the same
limits for the harness; targets the code doesn't meet yet don't gate.

Part of #44

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Yyy8fQGxPLkLa8v8NXz7T

Perf: the paged note list, by change, title and tag 1b398b0f48

dev now pages `notes.list` and filters by tag, so the harness measures
what the app asks for: a page of 50 newest first, A to Z, by tag, and 20
pages on through a cursor. A cold run is done when a one-note page counts
every note and the Home says its scan finished (`incomplete: false`).

Part of #44

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Yyy8fQGxPLkLa8v8NXz7T

Perf: the first request asks for a page, like the app c12dd7cb32

The request that opens the Home is now the first page of the note list
(`home.first_page`, gated). The old whole-Home list stays measured
(`home.first_list`, `home.list`) but only as a target: it is deprecated
and costs seconds at 100k notes.

Part of #44

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Yyy8fQGxPLkLa8v8NXz7T

Perf budgets: baseline on today's dev, budgets from it 16760e2367

dev gained the batched startup scan, paged lists and fan-out before the
disk while this was measured, which fixed four of the problems the first
baseline found. The page now holds the baseline at e2f4928 (5 warm and 3
cold runs at 1k, 10k and 100k notes), budgets set just above it, and the
problems still open: memory at 100k, the first request waiting for the
Home at 100k, a flat 51 ms first open, keystroke throughput.

Part of #44

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Yyy8fQGxPLkLa8v8NXz7T

Perf: idle CPU, wake-ups and memory; CPU while one person types

CI / rust (pull_request) Failing after 24s

Details

CI / web (pull_request) Failing after 10m31s

Details

b148e7a1a0

Once per Home size the harness now waits until the Home settled and every
room closed, then measures 5 idle minutes from /proc: CPU ticks, context
switches of every thread (wake-ups), RSS and threads. It also measures the
server's CPU and wake-ups while one person types five characters a second
with a second client watching. Budgets: idle CPU <= 0.1 %, wake-ups <=
0.2/s, typing CPU <= 2 % (gated); RSS at 100k <= 100 MB (target until
met). The server's stdout (its log) now goes to server.log.

Part of #44

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Yyy8fQGxPLkLa8v8NXz7T

Server: TCP_NODELAY on every connection

CI / rust (pull_request) Failing after 22s

Details

CI / web (pull_request) Failing after 10m29s

Details

bc53c03781

A reply the server writes in pieces (a room's "joined", then the note's
state) waited for the client's delayed ACK, about 40 ms, so opening any
note in the editor took at least that long; the perf harness showed a
flat ~51 ms first open at every Home size (#44). Every accepted
connection now sets TCP_NODELAY. Budget: open.note p95 <= 50 ms.

Part of #44

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Yyy8fQGxPLkLa8v8NXz7T

kayg referenced this pull request

2026-10-14 07:28:01 +00:00

Notes: a first open doesn't wait for the disk #182

kayg referenced this pull request

2026-10-14 07:28:36 +00:00

Server: TCP_NODELAY on every connection #117

kayg referenced this pull request

2026-10-14 08:04:52 +00:00

Server: TCP_NODELAY on every connection #192

kayg commented

2026-10-14 08:05:14 +00:00

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