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perf(start-client-core): O(1) buffer drain in client frame decoder - #7663
perf(start-client-core): O(1) buffer drain in client frame decoder#7663anonrig wants to merge 0 commit into
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📝 WalkthroughWalkthrough
ChangesFrame decoder O(1) buffer optimization
Estimated code review effort🎯 2 (Simple) | ⏱️ ~10 minutes Poem
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✏️ Tip: You can configure your own custom pre-merge checks in the settings. ✨ Finishing Touches🧪 Generate unit tests (beta)
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🧹 Nitpick comments (1)
packages/start-client-core/tests/frame-decoder.test.ts (1)
567-567: 🧹 Nitpick | 🔵 Trivial | ⚡ Quick winUse braces for one-line control statements in tests.
Line 567, Line 600-601, and Line 641 use single-line bodies without braces, which violates the project rule for TS/JS control flow.
As per coding guidelines, "
**/*.{ts,tsx,js,jsx}: Always use curly braces forif,else, loops, and similar control statements. Never write one-line bodies likeif (foo) x = 1."Suggested patch
- for (let i = 0; i < payload.length; i++) payload[i] = (i * 7) % 256+ for (let i = 0; i < payload.length; i++) {+ payload[i] = (i * 7) % 256+ } while (true) { const { done, value } = await rawReader.read() - if (done) break- if (value) received.push(...value)+ if (done) {+ break+ }+ if (value) {+ received.push(...value)+ } } while (true) { const { done, value } = await reader.read() - if (done) break+ if (done) {+ break+ } received.push(value) }Also applies to: 600-601, 641-641
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@packages/start-client-core/tests/frame-decoder.test.ts` at line 567, The for loop on line 567 with body payload[i] = (i * 7) % 256 uses a single-line body without braces, violating the project's coding guidelines. Add curly braces around the loop body to properly format it. Additionally, apply the same fix to the other single-line control statements mentioned at lines 600-601 and 641 by wrapping their bodies in curly braces.Source: Coding guidelines
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Nitpick comments:
In `@packages/start-client-core/tests/frame-decoder.test.ts`:
- Line 567: The for loop on line 567 with body payload[i] = (i * 7) % 256 uses a
single-line body without braces, violating the project's coding guidelines. Add
curly braces around the loop body to properly format it. Additionally, apply the
same fix to the other single-line control statements mentioned at lines 600-601
and 641 by wrapping their bodies in curly braces.
ℹ️ Review info
⚙️ Run configuration
Configuration used: defaults
Review profile: CHILL
Plan: Pro
Run ID: d9195414-0588-45d1-b334-36aea734698b
📒 Files selected for processing (3)
.changeset/perf-frame-decoder-index-pointer.mdpackages/start-client-core/src/client-rpc/frame-decoder.tspackages/start-client-core/tests/frame-decoder.test.ts
View your CI Pipeline Execution ↗ for commit 38c9d48
☁️ Nx Cloud last updated this comment at |
Merging this PR will not alter performance
|
| Mode | Benchmark | BASE | HEAD | Efficiency | |
|---|---|---|---|---|---|
| ❌ | Memory | mem serialization-payload (solid) | 6.9 MB | 7.4 MB | -5.96% |
| ⚡ | Memory | mem aborted-requests (solid) | 1.8 MB | 1.6 MB | +12.59% |
Tip
Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.
Comparing anonrig:perf/frame-decoder-index-pointer (38c9d48) with main (f23ed0f)1
Footnotes
Sheraff
commented
Jun 22, 2026
Can you fix the conflicts on this one? And then I'll merge it |
Sheraff
commented
Aug 8, 2026
38c9d48 to
f97188fCompare
What
Replace the O(n)
bufferList.shift()in the client-side frame decoder (packages/start-client-core/src/client-rpc/frame-decoder.ts) with an O(1) head pointer.extractFlattened()dropped each fully-consumed chunk from the front ofbufferListwithshift(). When a single large frame (e.g. a bigRawStreampayload) is assembled from many small network reads, the extract loop callsshift()once per chunk — and eachshift()re-indexes the whole array, so reassembly degrades to O(n²).This PR tracks the first un-consumed chunk with a
bufferHeadindex and advances it in O(1) instead of shifting.readHeader()reads frombufferHeadas well. Consumed slots are released for GC, and the array is compacted:bufferHead === bufferList.length) → reset in O(1) (the common terminal state), orsplice()it off (amortized O(1) per consumed chunk).This mirrors the index-pointer approach already used in
transformStreamWithRouterfor the same reason.Why
Same hot path as the sibling zero-copy PR: decoding streamed server-function responses and
RawStreampayloads. The O(n²) bites specifically when one frame spans many buffered chunks.Standalone micro-benchmark (Node, median of 12 runs), draining N buffered chunks:
shift()Tests
frame-decodersuite passes.CHUNKpayload delivered one byte at a time (forces the header slow path + many whole-chunk consumptions + the fully-drained reset),splice()prefix drop).Notes
extractFlattened, so whichever merges second will need a trivial rebase.@tanstack/start-client-corepatch).Summary by CodeRabbit
Performance
Tests