Move task encoding to save_snapshot for parallel encoding and buffer reuse #88924

lukesandberg · 2026-01-23T02:23:54Z

What

Change when TaskStorage encoding happens so it can happen in parallel as we accumulate data for the sst files.

Why

Currently encoding for a snapshot happens in a single thread when iterating the 'snapshot shards'. Encoding allocates a lot of memory into temporary buffers and then we organize it into files in parallel.

By deferring slightly when encoding happens we can

reuse a scratch buffer to avoid dynamic resizes of small_vecs in the common case
reduce the max amount of memory that is allocated for writing since now we allocate the buffers as we are about to write out files.

lukesandberg · 2026-01-23T02:24:13Z

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vercel

Additional Suggestion:

Missing pattern match for CollectorEntryValue::Tiny variant causes verification to panic when encountering tiny values

codspeed-hq · 2026-01-23T02:45:05Z

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing cache_task_stats (ff6b6d5) with canary (cedfb53)}

Summary

✅ 17 untouched benchmarks
⏩ 3 skipped benchmarks¹

3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

nextjs-bot · 2026-01-23T02:45:19Z

Stats from current PR

✅ No significant changes detected

📊 All Metrics

📖 Metrics Glossary

Dev Server Metrics:

Listen = TCP port starts accepting connections
First Request = HTTP server returns successful response
Cold = Fresh build (no cache)
Warm = With cached build artifacts

Build Metrics:

Fresh = Clean build (no .next directory)
Cached = With existing .next directory

Change Thresholds:

Time: Changes < 50ms AND < 10%, OR < 2% are insignificant
Size: Changes < 1KB AND < 1% are insignificant
All other changes are flagged to catch regressions

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	456ms	455ms	✓	▅▅▅▁▁
Cold (Ready in log)	438ms	438ms	✓	▇▇▆▇█
Cold (First Request)	1.831s	1.827s	✓	▆▅▅█▆
Warm (Listen)	456ms	455ms	✓	███▁▁
Warm (Ready in log)	438ms	438ms	✓	▄▅▅█▆
Warm (First Request)	1.859s	1.849s	✓	▅▄▅█▅

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	14.175s	14.050s	✓	▄▃▃▇▃
Cached Build	14.212s	14.252s	✓	▃▃▂▆▃
node_modules Size	461 MB	461 MB	✓	▁▁▁██

📦 Bundle Sizes

Bundle Sizes

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
2086.HASH.js gzip	169 B	N/A	-
2161-HASH.js gzip	5.41 kB	N/A	-
2747-HASH.js gzip	4.48 kB	N/A	-
4322-HASH.js gzip	52.7 kB	N/A	-
ec793fe8-HASH.js gzip	62.3 kB	N/A	-
framework-HASH.js gzip	59.8 kB	59.8 kB	✓
main-app-HASH.js gzip	251 B	253 B	✓
main-HASH.js gzip	38.7 kB	39.1 kB	✓
webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
1596.HASH.js gzip	N/A	169 B	-
2658-HASH.js gzip	N/A	52.4 kB	-
6349-HASH.js gzip	N/A	4.46 kB	-
7019-HASH.js gzip	N/A	5.43 kB	-
b17a3386-HASH.js gzip	N/A	62.3 kB	-
Total	226 kB	226 kB	⚠️ +54 B

Polyfills

	Canary	PR	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Total	39.4 kB	39.4 kB	✓

Pages

	Canary	PR	Change
_app-HASH.js gzip	194 B	193 B	✓
_error-HASH.js gzip	182 B	182 B	✓
css-HASH.js gzip	336 B	335 B	✓
dynamic-HASH.js gzip	1.8 kB	1.8 kB	✓
edge-ssr-HASH.js gzip	256 B	256 B	✓
head-HASH.js gzip	352 B	349 B	✓
hooks-HASH.js gzip	385 B	384 B	✓
image-HASH.js gzip	580 B	580 B	✓
index-HASH.js gzip	259 B	258 B	✓
link-HASH.js gzip	2.5 kB	2.51 kB	✓
routerDirect..HASH.js gzip	319 B	317 B	✓
script-HASH.js gzip	385 B	387 B	✓
withRouter-HASH.js gzip	316 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	7.97 kB	7.96 kB	✅ -8 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	126 kB	126 kB	✓
page.js gzip	244 kB	240 kB	🟢 4.51 kB (-2%)
Total	371 kB	366 kB	✅ -4.63 kB

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	617 B	616 B	✓
middleware-r..fest.js gzip	155 B	156 B	✓
middleware.js gzip	33 kB	33.2 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.6 kB	34.9 kB	⚠️ +237 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	738 B	738 B	✓
Total	738 B	738 B	✓

Build Cache

	Canary	PR	Change
0.pack gzip	3.71 MB	3.72 MB	🔴 +7.68 kB (+0%)
index.pack gzip	102 kB	102 kB	✓
index.pack.old gzip	102 kB	102 kB	✓
Total	3.92 MB	3.92 MB	⚠️ +7.12 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	306 kB	306 kB	✓
app-page-exp..prod.js gzip	163 kB	163 kB	✓
app-page-tur...dev.js gzip	306 kB	306 kB	✓
app-page-tur..prod.js gzip	163 kB	163 kB	✓
app-page-tur...dev.js gzip	303 kB	303 kB	✓
app-page-tur..prod.js gzip	161 kB	161 kB	✓
app-page.run...dev.js gzip	303 kB	303 kB	✓
app-page.run..prod.js gzip	161 kB	161 kB	✓
app-route-ex...dev.js gzip	69.4 kB	69.4 kB	✓
app-route-ex..prod.js gzip	48.2 kB	48.2 kB	✓
app-route-tu...dev.js gzip	69.5 kB	69.5 kB	✓
app-route-tu..prod.js gzip	48.2 kB	48.2 kB	✓
app-route-tu...dev.js gzip	69.1 kB	69.1 kB	✓
app-route-tu..prod.js gzip	48 kB	48 kB	✓
app-route.ru...dev.js gzip	69 kB	69 kB	✓
app-route.ru..prod.js gzip	48 kB	48 kB	✓
dist_client_...dev.js gzip	324 B	324 B	✓
dist_client_...dev.js gzip	326 B	326 B	✓
dist_client_...dev.js gzip	318 B	318 B	✓
dist_client_...dev.js gzip	317 B	317 B	✓
pages-api-tu...dev.js gzip	42.5 kB	42.5 kB	✓
pages-api-tu..prod.js gzip	32.3 kB	32.3 kB	✓
pages-api.ru...dev.js gzip	42.5 kB	42.5 kB	✓
pages-api.ru..prod.js gzip	32.3 kB	32.3 kB	✓
pages-turbo....dev.js gzip	51.8 kB	51.8 kB	✓
pages-turbo...prod.js gzip	38.8 kB	38.8 kB	✓
pages.runtim...dev.js gzip	51.8 kB	51.8 kB	✓
pages.runtim..prod.js gzip	38.8 kB	38.8 kB	✓
server.runti..prod.js gzip	62.3 kB	62.3 kB	✓
Total	2.73 MB	2.73 MB	✅ -3 B

- Add Tiny variant for inline storage of values ≤22 bytes (no heap allocation) - Change Small/Medium to use Box<[u8]> instead of SmallVec/Vec - Simplify ValueBuffer API with single into_boxed_slice() method - Add TODO comment about work distribution fairness in write_batch Co-Authored-By: Claude <[email protected]>

nextjs-bot added created-by: Turbopack team PRs by the Turbopack team. Turbopack Related to Turbopack with Next.js. labels Jan 23, 2026

lukesandberg mentioned this pull request Jan 23, 2026

[turbopack] add task type infromation to the print_cache_item_size feature #88925

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vercel bot reviewed Jan 23, 2026

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lukesandberg and others added 2 commits January 22, 2026 23:38

use a shared scratch buffer when encoding task values

ff6b6d5

lukesandberg force-pushed the cache_task_stats branch from 866e2c8 to ff6b6d5 Compare January 23, 2026 08:38

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Move task encoding to save_snapshot for parallel encoding and buffer reuse #88924

Move task encoding to save_snapshot for parallel encoding and buffer reuse #88924

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