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Turbopack: Very minor improvements for watcher loop#96103

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bgw merged 1 commit into
bgw/refactor-watcher-batchfrom
bgw/minor-watcher-cleanup
Jul 23, 2026
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Turbopack: Very minor improvements for watcher loop#96103
bgw merged 1 commit into
bgw/refactor-watcher-batchfrom
bgw/minor-watcher-cleanup

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@bgw

@bgw bgw commented Jul 23, 2026

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Noticed these things while reading through the code.

@github-actions

github-actions Bot commented Jul 23, 2026

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Stats from current PR

🟢 2 improvements

Metric Canary PR Change Trend
Webpack Cold (First Request) 3.411s 3.304s 🟢 107ms (-3%) ▁▂▃▂█
Webpack Warm (First Request) 3.415s 3.253s 🟢 162ms (-5%) ▁▂▁▁█
📊 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

Metric Canary PR Change Trend
Cold (Listen) 1.064s 1.064s ▁▂▂██
Cold (Ready in log) 1.036s 1.029s ▁▁▁██
Cold (First Request) 1.686s 1.687s ▁▂▁██
Warm (Listen) 1.064s 1.064s ▁▂▂██
Warm (Ready in log) 1.033s 1.027s ▁▂▁██
Warm (First Request) 1.687s 1.678s ▁▁▁██
📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric Canary PR Change Trend
Cold (Listen) 813ms 760ms ▁████
Cold (Ready in log) 775ms 756ms ▁█▃▆▆
Cold (First Request) 3.411s 3.304s 🟢 107ms (-3%) ▁▂▃▂█
Warm (Listen) 811ms 759ms █████
Warm (Ready in log) 774ms 752ms ▂█▃▁▇
Warm (First Request) 3.415s 3.253s 🟢 162ms (-5%) ▁▂▁▁█

⚡ Production Builds

Metric Canary PR Change Trend
Fresh Build 7.086s 7.056s ▁▁▁██
Cached Build 7.138s 7.106s ▁▂▁██
📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric Canary PR Change Trend
Fresh Build 25.191s 25.067s ▁▂▃▃█
Cached Build 25.346s 25.002s ▂▁▅▄▅
node_modules Size 527 MB 527 MB █████
📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles
Canary PR Change
03v9blsp0psjq.js gzip 71.1 kB N/A -
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1h--jlxvyq3f_.js gzip 160 B N/A -
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1tf1phijqlx9j.js gzip 220 B 220 B
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28koph4jjzmen.js gzip 45.2 kB N/A -
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turbopack-1h..cctz.js gzip 3.81 kB N/A -
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turbopack-2x..j7tp.js gzip 3.82 kB N/A -
turbopack-31..0owl.js gzip 3.81 kB N/A -
turbopack-34..cuoy.js gzip 3.81 kB N/A -
turbopack-36..7fxt.js gzip 3.81 kB N/A -
turbopack-3x..rb-n.js gzip 3.81 kB N/A -
turbopack-44..7z5z.js gzip 3.8 kB N/A -
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030a1njeh5b77.js gzip N/A 10 kB -
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186r3y_rfvr0b.js gzip N/A 8.78 kB -
19v97848yrjp7.js gzip N/A 8.81 kB -
1cvaplh7gszio.js gzip N/A 157 B -
1l-r8anpd80-7.js gzip N/A 71.1 kB -
1nd_0rwgz2ozk.js gzip N/A 9.45 kB -
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1rq1g_cwv642d.js gzip N/A 10.3 kB -
1uojw_uabeg93.js gzip N/A 450 B -
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341h71ln1jpl3.js gzip N/A 2.29 kB -
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36ckfq9o-ys-a.js gzip N/A 13.1 kB -
3vdh6_u50pu5t.js gzip N/A 13.6 kB -
turbopack-0_..mu2p.js gzip N/A 3.81 kB -
turbopack-0g..ecs7.js gzip N/A 3.8 kB -
turbopack-0l..-gfw.js gzip N/A 3.82 kB -
turbopack-0x..bwoh.js gzip N/A 3.81 kB -
turbopack-12..bane.js gzip N/A 3.81 kB -
turbopack-15..7p35.js gzip N/A 3.81 kB -
turbopack-1l..lxas.js gzip N/A 3.8 kB -
turbopack-1s..3rf-.js gzip N/A 3.78 kB -
turbopack-1x..6i4w.js gzip N/A 3.81 kB -
turbopack-22..hey9.js gzip N/A 3.81 kB -
turbopack-28..ue4z.js gzip N/A 3.81 kB -
turbopack-2h..5bop.js gzip N/A 3.81 kB -
turbopack-36..s8xy.js gzip N/A 3.8 kB -
turbopack-3q..fot4.js gzip N/A 3.81 kB -
Total 448 kB 448 kB ⚠️ +52 B

Server

Middleware
Canary PR Change
middleware-b..fest.js gzip 776 B 775 B
Total 776 B 775 B ✅ -1 B
Build Details
Build Manifests
Canary PR Change
_buildManifest.js gzip 434 B 432 B
Total 434 B 432 B ✅ -2 B

📦 Webpack

Client

Main Bundles
Canary PR Change
3322-HASH.js gzip 63.7 kB N/A -
4191.HASH.js gzip 169 B N/A -
7920-HASH.js gzip 4.68 kB N/A -
9784-HASH.js gzip 5.63 kB N/A -
b1ad9f4c-HASH.js gzip 62.9 kB N/A -
framework-HASH.js gzip 59.7 kB 59.7 kB
main-app-HASH.js gzip 254 B 253 B
main-HASH.js gzip 40 kB 40 kB
webpack-HASH.js gzip 1.68 kB 1.68 kB
3577.HASH.js gzip N/A 168 B -
578-HASH.js gzip N/A 64.4 kB -
8590-HASH.js gzip N/A 5.61 kB -
9750-HASH.js gzip N/A 4.69 kB -
a8984546-HASH.js gzip N/A 62.9 kB -
Total 239 kB 239 kB ⚠️ +636 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 181 B 182 B
css-HASH.js gzip 334 B 331 B
dynamic-HASH.js gzip 1.81 kB 1.81 kB
edge-ssr-HASH.js gzip 255 B 253 B
head-HASH.js gzip 349 B 351 B
hooks-HASH.js gzip 382 B 384 B
image-HASH.js gzip 581 B 582 B
index-HASH.js gzip 260 B 259 B
link-HASH.js gzip 2.48 kB 2.48 kB
routerDirect..HASH.js gzip 317 B 318 B
script-HASH.js gzip 384 B 386 B
withRouter-HASH.js gzip 316 B 315 B
1afbb74e6ecf..834.css gzip 106 B 106 B
Total 7.95 kB 7.95 kB ⚠️ +1 B

Server

Edge SSR
Canary PR Change
edge-ssr.js gzip 128 kB 128 kB
page.js gzip 287 kB 287 kB
Total 415 kB 414 kB ✅ -879 B
Middleware
Canary PR Change
middleware-b..fest.js gzip 618 B 616 B
middleware-r..fest.js gzip 156 B 156 B
middleware.js gzip 45.3 kB 45 kB
edge-runtime..pack.js gzip 842 B 842 B
Total 46.9 kB 46.6 kB ✅ -262 B
Build Details
Build Manifests
Canary PR Change
_buildManifest.js gzip 718 B 718 B
Total 718 B 718 B
Build Cache
Canary PR Change
0.pack gzip 4.84 MB 4.84 MB 🟢 4.86 kB (0%)
index.pack gzip 120 kB 120 kB
index.pack.old gzip 120 kB 120 kB
Total 5.08 MB 5.08 MB ✅ -5.84 kB

🔄 Shared (bundler-independent)

Runtimes
Canary PR Change
app-page-exp...dev.js gzip 366 kB 366 kB
app-page-exp..prod.js gzip 202 kB 202 kB
app-page-tur...dev.js gzip 365 kB 365 kB
app-page-tur..prod.js gzip 202 kB 202 kB
app-page-tur...dev.js gzip 362 kB 362 kB
app-page-tur..prod.js gzip 200 kB 200 kB
app-page.run...dev.js gzip 362 kB 362 kB
app-page.run..prod.js gzip 200 kB 200 kB
app-route-ex...dev.js gzip 81.8 kB 81.8 kB
app-route-ex..prod.js gzip 55.6 kB 55.6 kB
app-route-tu...dev.js gzip 81.8 kB 81.8 kB
app-route-tu..prod.js gzip 55.6 kB 55.6 kB
app-route-tu...dev.js gzip 81.4 kB 81.4 kB
app-route-tu..prod.js gzip 55.4 kB 55.4 kB
app-route.ru...dev.js gzip 81.4 kB 81.4 kB
app-route.ru..prod.js gzip 55.4 kB 55.4 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 45.4 kB 45.4 kB
pages-api-tu..prod.js gzip 34.1 kB 34.1 kB
pages-api.ru...dev.js gzip 45.4 kB 45.4 kB
pages-api.ru..prod.js gzip 34.1 kB 34.1 kB
pages-turbo....dev.js gzip 54.9 kB 54.9 kB
pages-turbo...prod.js gzip 39.7 kB 39.7 kB
pages.runtim...dev.js gzip 54.8 kB 54.8 kB
pages.runtim..prod.js gzip 39.7 kB 39.7 kB
server.runti..prod.js gzip 67.8 kB 67.8 kB
use-cache-pr...dev.js gzip 71.6 kB 71.6 kB
use-cache-pr...dev.js gzip 71.6 kB 71.6 kB
use-cache-pr...dev.js gzip 69.9 kB 69.9 kB
use-cache-pr...dev.js gzip 69.9 kB 69.9 kB
Total 3.51 MB 3.51 MB
📎 Tarball URL
https://vercel-packages.vercel.app/next/commits/95d018be75016461f3461a09c4e78db8899b421c/next

Commit: 95d018b

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github-actions Bot commented Jul 23, 2026

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Tests Passed

Commit: 95d018b

@bgw
bgw force-pushed the bgw/minor-watcher-cleanup branch from 102a417 to 95d018b Compare July 23, 2026 18:35
Comment on lines +511 to +513
// flush the whole mpsc queue, we're about to rescan, we don't need to
// process any other update events that have already happened
while rx.try_recv().is_ok() {}

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Minor perf improvement if we're forced to do a full rescan. Might be good because a rescan event already likely indicates that the system is overloaded.

// For the rename::both, notify provides an array of paths
// in given order
if let [source, destination, ..] = &paths[..] {
if let [source, destination] = &paths[..] {

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This event should always be exactly two paths.
https://docs.rs/notify/latest/notify/event/enum.RenameMode.html#variant.Both

This event should be emitted when both source and target are known. The paths should be provided in this exact order (from, to).

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thanks, i was wondering about this in the other PR

// but we also check other RenameModes to cover cases where notify couldn't match the
// two rename events.
EventKind::Any | EventKind::Modify(ModifyKind::Any | ModifyKind::Name(..)) => {
self.path.extend(paths.clone());

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path is already covered by path_and_children.

@bgw
bgw marked this pull request as ready for review July 23, 2026 19:59
@bgw
bgw requested a review from a team July 23, 2026 19:59
@bgw
bgw disabled auto-merge July 23, 2026 23:17
@bgw
bgw merged commit 82934fc into canary Jul 23, 2026
228 of 230 checks passed
@bgw
bgw deleted the bgw/minor-watcher-cleanup branch July 23, 2026 23:18

@gdoogamal37-prog gdoogamal37-prog left a comment

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Ok

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3 participants