Thomas Camlong
2ebfe659b2
Both patches came out of this work and both are removed at the maintainer's request. The finding was real - ssh2's WASM heap costs +14.0 MiB RSS on require, and @grpc/grpc-js another 14.6 MiB across 61 files, neither of which a socket-based Docker install ever uses - but patching a dependency means every future dockerode or docker-modem bump fails until someone regenerates the patch, and that recurring cost is not worth roughly 25 MiB. The finding stays on record in SERVER-MEMORY.md because the fix belongs upstream: both packages require a module at file scope while using it in exactly one already-guarded branch, so a PR to each would fix it for every consumer with no patch to maintain here. The two remaining patches, @types/node-unifi and trpc-to-openapi, predate this work and are untouched. allowUnusedPatches was already set on dev and is left alone. Lockfile regenerated: patchedDependencies now lists only those two. Also sharpens the Cache Components entry. The SqliteError was simply an unmigrated build database, which is fixable - but feeding the build a database would be the wrong fix, because serverSetting is per-installation data on the user's volume and a shell prerendered against the build machine's database would bake one install's settings into every other install's first paint. The error was Next.js correctly reporting a request-time read sitting in the shell path.
139 lines
8.2 KiB
Markdown
139 lines
8.2 KiB
Markdown
# Where this left off, and what to do next
|
||
|
||
Written as a handoff. The branch is green and everything below is measured except where explicitly
|
||
marked.
|
||
|
||
## 1. Verify the unmeasured changes
|
||
|
||
Four commits apply the off-screen-row treatment beyond the one widget where it was measured. All are
|
||
typechecked and lint-clean, none are A/B'd — they are the only performance claims on this branch not
|
||
verified before commit.
|
||
|
||
| commit | widget | measured on this board? |
|
||
| --- | --- | --- |
|
||
| `7550766f6` | mediaReleases | **yes** — 135 → 55 image requests, 8346 → 5117 layout objects |
|
||
| `c526dd2b7` | mediaRequests-requestList | no — but overdraw confirmed: 1,512 px of cards in a 405 px tile, 60 images |
|
||
| `040f10594` | rssFeed, notifications, calendar event list | no — these do **not** overdraw on this board |
|
||
|
||
The last row needs care when reading a result. On the test backup rssFeed renders 7 nodes and the
|
||
calendar's 7 rows fit their tile, so a measurement will correctly show **no change**. That is not a
|
||
failure of the change — the benefit only exists for a user whose integrations return more rows than
|
||
the tile can show. To observe it, use a backup with a busier feed, or shrink the tile.
|
||
|
||
For `c526dd2b7`, which does overdraw here, a real effect is expected:
|
||
|
||
```bash
|
||
# restore two containers on identical data, one per image, then:
|
||
STRESS_BASE_URL=http://127.0.0.1:PORT STRESS_BOARD=default \
|
||
node --experimental-strip-types scripts/benchmarks/measure-board-paint.mts
|
||
```
|
||
|
||
Expect **image requests to fall**. Do **not** expect JS heap to move: decoded bitmaps live outside
|
||
`JSHeapUsedSize`. Three repeats per side — a single run wrongly suggested a −16% heap win on the first
|
||
widget. If image requests do not fall, revert it.
|
||
|
||
## 1b. What was deliberately not changed
|
||
|
||
26 widgets use `ScrollArea`; the treatment was applied to five. `content-visibility` is not free — it
|
||
costs containment work, and on content that measures itself (charts, editors, the notebook) skipping
|
||
layout can be actively wrong. The rule used: apply it where list length is decided by remote data,
|
||
leave fixed-size and chart widgets alone.
|
||
|
||
`beszelSystemStats`, `beszelSystemTable` and `beszelSystemGrid` report large row counts in the
|
||
overdraw tool, but that is the tool misreading SVG groups as rows — their content fits their tiles.
|
||
|
||
## React `cache()` and memoisation — already in place
|
||
|
||
Recorded because it looks like a gap and is not.
|
||
|
||
React `cache()` is **server-only**: it dedupes within a single RSC render and does nothing for client
|
||
widget rendering. It is already applied where it belongs — `getBoardByNameAsync`, `getHomeBoardAsync`,
|
||
`getRscServerSettingsAsync` and `getQueryClient` are all wrapped, the last with a comment explaining
|
||
the dedup.
|
||
|
||
Client-side data is cached by tRPC/react-query, whose `gcTime` was already checked and found to be
|
||
5 minutes, not the 24 hours the original fix catalogue assumed. `React.memo` is already used in the
|
||
clock, calendar and releases widgets.
|
||
|
||
## 2. The one lever with real headroom left
|
||
|
||
**The tRPC router imports every integration eagerly.** A single **16.10 MiB subtree of 460 files** is
|
||
reached by every API route, and because Next preloads route bundles it is resident before the first
|
||
request. This pays twice:
|
||
|
||
- ~41 MiB of retained bundle source (28% of the live server heap) — V8 keeps a script's source alive
|
||
while any function in it may still be lazily compiled
|
||
- ~38 MiB of V8 compiler zone memory, which is **proportional to how much JavaScript V8 compiles** and
|
||
is not reachable by any V8 flag (`--max-opt` is a null result; only `--jitless` removes it, and that
|
||
breaks rendering)
|
||
|
||
Nothing else has this profile. Every allocator and V8-level avenue is closed — see
|
||
[REJECTED.md](./REJECTED.md).
|
||
|
||
Start from `analyze-require-graph.mjs`, which found the shared subtree, and
|
||
`[root-of-the-server]__0g06wx7._.js` as the chunk reaching 460 files.
|
||
|
||
## 3. Known-good but deliberately deferred
|
||
|
||
| item | prize | why it was not done |
|
||
| --- | --- | --- |
|
||
| ASCII-escape server bundles | **9.45 MiB** | Proven mechanism — 2.00 vs 1.00 bytes/char; one char above U+00FF doubles a whole source string. Needs a build-time rewrite of minified **vendor** output, so it deserves its own PR and safety argument |
|
||
| Lazy `mysql2` / `pg` | 21.4 MiB | Three implementations, all broken; see REJECTED.md. Structurally blocked because `createDb` must stay synchronous |
|
||
| `beszelSystemStats` at 1,156 nodes | unknown | Second-heaviest widget, but its cost is chart SVG (`<g>×317`), so reducing it changes what is drawn |
|
||
| `documents` reads 18–32 | unknown | Never investigated; each document carries overhead |
|
||
|
||
## 4. For the clean PR
|
||
|
||
The instruction was to close this experimental PR and open one with only the verified fixes, judged on
|
||
lines-of-code to performance ratio. On the evidence, that set is:
|
||
|
||
| change | size | measured effect |
|
||
| --- | --- | --- |
|
||
| `--max-semi-space-size=4` | **1 line** | −19% idle, −21% peak |
|
||
| `preloadEntriesOnStart: false` | **1 line** | −52% anon at idle; 310 fewer files even at full load |
|
||
| Umami: stop fetching 100k raw events per refresh | 1 file | −26% peak, −93% transient buffers, largest allocation 46.4 → 2.4 MiB |
|
||
| `serverExternalPackages` (mysql2/pg + 8 more) | 1 block | −21 MiB idle |
|
||
| `content-visibility` on media-release cards | 4 lines | −59% image requests, −41% layout objects |
|
||
| ~~ssh2 WASM heap (docker-modem patch)~~ | ~~1 patch~~ | **dropped** — the gain was real (−15 to −18 MiB external) but patching a dependency breaks on every `dockerode`/`docker-modem` bump. Worth raising upstream instead: both packages require a module at file scope while using it in one already-guarded branch |
|
||
| Reuse the certificate agent instead of one per request | 1 file | 5.11 → 1.69 ms/request, 60 → 2 TLS handshakes over 60 requests |
|
||
| Stream proxied images instead of buffering | 2 files | −36% peak RSS on 30 concurrent 2 MiB images (116 → 74 MiB) |
|
||
|
||
Together the server changes produce the headline: **−26% peak anon, −52% at idle**, no overlapping
|
||
ranges at any stage, for **+18% CPU**.
|
||
|
||
Two notes for whoever cuts it:
|
||
|
||
- **Split the formatting out of `media-missing/component.tsx`.** Its 77-line diff is roughly 8 lines of
|
||
semantic change plus **69 lines of pre-existing formatting debt** that `oxfmt` swept up when the file
|
||
was touched. Every other file changed in this work was already `oxfmt`-clean, so this is the only one
|
||
affected. Landing the reformat as its own commit keeps the perf change reviewable.
|
||
- The client changes worth carrying are `OverflowBadge`, the `calendar` day-cell `HoverCard`, the
|
||
`beszelSystemTable` inline `PercentCell`, `content-visibility` on the data-driven lists, the two
|
||
`keepMounted={false}` widgets, and the `placehold.co` removal. The last of those is a bug fix rather
|
||
than an optimisation and should probably ship regardless.
|
||
|
||
Two things to leave out or flag:
|
||
|
||
- **The gRPC patch** removes 112 files and 6 MiB from an isolated `require`, but is **not separately
|
||
visible in a full run**. Bundle hygiene, not a measured memory win.
|
||
- **Median board load reads +30%** but is **not established** — individual loads were
|
||
[506, 383, 1233] and [848, 431, 574] before against [780, 808, 515] and [621, 579, 1004] after,
|
||
heavily overlapping with no cold-then-warm pattern. If the latency trade matters, measure it properly
|
||
with many more samples; the suspicion is that it is real and concentrated in
|
||
`preloadEntriesOnStart`.
|
||
|
||
## 5. Read this before measuring anything
|
||
|
||
[METHODOLOGY.md](./METHODOLOGY.md). Every wrong number in this investigation came from an instrument,
|
||
not the application, and several were published before being caught. The short version:
|
||
|
||
- a heap snapshot **cannot** explain a peak — V8 GCs first and reports survivors only
|
||
- V8 truncates snapshot string contents to ~1 KiB
|
||
- snapshot objects are **not** live native handles
|
||
- measuring without a forced GC measures V8's growth, not a module's cost
|
||
- taking a CDP heap snapshot added **134 MiB to the process being measured**
|
||
- React per-component attribution silently returns **nothing** on a production build
|
||
- a fixed port can measure a **leftover container**
|
||
- **when a server-side change moves a client-side metric, the workload changed** — this is how
|
||
`--jitless` was caught faking a 24% win by under-rendering the page
|