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Fix memory leak hotspots#5116

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JoviDeCroock merged 1 commit into
v10.xfrom
JoviDeCroock/fix-memory-leak-hotspots
Jun 15, 2026
Merged

Fix memory leak hotspots#5116
JoviDeCroock merged 1 commit into
v10.xfrom
JoviDeCroock/fix-memory-leak-hotspots

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@JoviDeCroock

@JoviDeCroock JoviDeCroock commented Jun 12, 2026 •
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Local replace1k check: run-final 10.99ms vs 10.79ms main, overlapping CI.

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📊 Tachometer Benchmark Results

Summary

duration

  • create10k: unsure 🔍 -1% - +0% (-5.06ms - +1.18ms)
    preact-local vs preact-main
  • filter-list: unsure 🔍 -1% - +0% (-0.15ms - +0.05ms)
    preact-local vs preact-main
  • hydrate1k: unsure 🔍 -2% - +1% (-1.19ms - +0.29ms)
    preact-local vs preact-main
  • many-updates: unsure 🔍 -0% - +0% (-0.04ms - +0.04ms)
    preact-local vs preact-main
  • replace1k: unsure 🔍 -1% - +1% (-0.78ms - +0.80ms)
    preact-local vs preact-main
  • text-update: unsure 🔍 -1% - +8% (-0.02ms - +0.15ms)
    preact-local vs preact-main
  • todo: unsure 🔍 -2% - +1% (-0.53ms - +0.36ms)
    preact-local vs preact-main
  • update10th1k: unsure 🔍 -7% - +1% (-1.76ms - +0.33ms)
    preact-local vs preact-main

usedJSHeapSize

  • create10k: unsure 🔍 +0% - +0% (+0.00ms - +0.00ms)
    preact-local vs preact-main
  • filter-list: unsure 🔍 -0% - +0% (-0.00ms - +0.00ms)
    preact-local vs preact-main
  • hydrate1k: unsure 🔍 -5% - +4% (-0.25ms - +0.19ms)
    preact-local vs preact-main
  • many-updates: unsure 🔍 -0% - +0% (-0.00ms - +0.00ms)
    preact-local vs preact-main
  • replace1k: unsure 🔍 -0% - +0% (-0.00ms - +0.01ms)
    preact-local vs preact-main
  • text-update: unsure 🔍 -5% - +2% (-0.06ms - +0.02ms)
    preact-local vs preact-main
  • todo: unsure 🔍 +0% - +0% (+0.00ms - +0.00ms)
    preact-local vs preact-main
  • update10th1k: unsure 🔍 -0% - +0% (-0.01ms - +0.00ms)
    preact-local vs preact-main

Results

create10k

duration

VersionAvg timevs preact-localvs preact-main
preact-local830.79ms - 835.13ms-unsure 🔍
-1% - +0%
-5.06ms - +1.18ms
preact-main832.65ms - 837.14msunsure 🔍
-0% - +1%
-1.18ms - +5.06ms		-

usedJSHeapSize

VersionAvg timevs preact-localvs preact-main
preact-local19.21ms - 19.21ms-unsure 🔍
+0% - +0%
+0.00ms - +0.00ms
preact-main19.21ms - 19.21msunsure 🔍
-0% - -0%
-0.00ms - -0.00ms		-
filter-list

duration

VersionAvg timevs preact-localvs preact-main
preact-local16.57ms - 16.65ms-unsure 🔍
-1% - +0%
-0.15ms - +0.05ms
preact-main16.57ms - 16.75msunsure 🔍
-0% - +1%
-0.05ms - +0.15ms		-

usedJSHeapSize

VersionAvg timevs preact-localvs preact-main
preact-local1.57ms - 1.57ms-unsure 🔍
-0% - +0%
-0.00ms - +0.00ms
preact-main1.57ms - 1.57msunsure 🔍
-0% - +0%
-0.00ms - +0.00ms		-
hydrate1k

duration

VersionAvg timevs preact-localvs preact-main
preact-local55.57ms - 56.58ms-unsure 🔍
-2% - +1%
-1.19ms - +0.29ms
preact-main55.98ms - 57.07msunsure 🔍
-1% - +2%
-0.29ms - +1.19ms		-

usedJSHeapSize

VersionAvg timevs preact-localvs preact-main
preact-local5.07ms - 5.34ms-unsure 🔍
-5% - +4%
-0.25ms - +0.19ms
preact-main5.06ms - 5.40msunsure 🔍
-4% - +5%
-0.19ms - +0.25ms		-
many-updates

duration

VersionAvg timevs preact-localvs preact-main
preact-local16.52ms - 16.57ms-unsure 🔍
-0% - +0%
-0.04ms - +0.04ms
preact-main16.52ms - 16.57msunsure 🔍
-0% - +0%
-0.04ms - +0.04ms		-

usedJSHeapSize

VersionAvg timevs preact-localvs preact-main
preact-local3.73ms - 3.73ms-unsure 🔍
-0% - +0%
-0.00ms - +0.00ms
preact-main3.73ms - 3.73msunsure 🔍
-0% - +0%
-0.00ms - +0.00ms		-
replace1k
  • Browser: chrome-headless
  • Sample size: 100
  • Built by: CI #5567

  • Commit: 5670ac8

duration

VersionAvg timevs preact-localvs preact-main
preact-local55.49ms - 56.65ms-unsure 🔍
-1% - +1%
-0.78ms - +0.80ms
preact-main55.52ms - 56.60msunsure 🔍
-1% - +1%
-0.80ms - +0.78ms		-

usedJSHeapSize

VersionAvg timevs preact-localvs preact-main
preact-local3.02ms - 3.02ms-unsure 🔍
-0% - +0%
-0.00ms - +0.01ms
preact-main3.01ms - 3.02msunsure 🔍
-0% - +0%
-0.01ms - +0.00ms		-

run-warmup-0

VersionAvg timevs preact-localvs preact-main
preact-local27.29ms - 27.92ms-unsure 🔍
-3% - +1%
-0.78ms - +0.19ms
preact-main27.53ms - 28.26msunsure 🔍
-1% - +3%
-0.19ms - +0.78ms		-

run-warmup-1

VersionAvg timevs preact-localvs preact-main
preact-local31.69ms - 32.69ms-unsure 🔍
-2% - +2%
-0.57ms - +0.79ms
preact-main31.63ms - 32.53msunsure 🔍
-2% - +2%
-0.79ms - +0.57ms		-

run-warmup-2

VersionAvg timevs preact-localvs preact-main
preact-local32.16ms - 33.40ms-unsure 🔍
-2% - +3%
-0.57ms - +1.09ms
preact-main31.97ms - 33.08msunsure 🔍
-3% - +2%
-1.09ms - +0.57ms		-

run-warmup-3

VersionAvg timevs preact-localvs preact-main
preact-local25.57ms - 25.98ms-unsure 🔍
-2% - +0%
-0.59ms - +0.11ms
preact-main25.73ms - 26.29msunsure 🔍
-0% - +2%
-0.11ms - +0.59ms		-

run-warmup-4

VersionAvg timevs preact-localvs preact-main
preact-local22.49ms - 23.54ms-unsure 🔍
-2% - +4%
-0.47ms - +1.01ms
preact-main22.22ms - 23.28msunsure 🔍
-4% - +2%
-1.01ms - +0.47ms		-

run-final

VersionAvg timevs preact-localvs preact-main
preact-local21.08ms - 21.46ms-unsure 🔍
-1% - +1%
-0.30ms - +0.20ms
preact-main21.16ms - 21.49msunsure 🔍
-1% - +1%
-0.20ms - +0.30ms		-
text-update
  • Browser: chrome-headless
  • Sample size: 230
  • Built by: CI #5567

  • Commit: 5670ac8

duration

VersionAvg timevs preact-localvs preact-main
preact-local2.00ms - 2.13ms-unsure 🔍
-1% - +8%
-0.02ms - +0.15ms
preact-main1.94ms - 2.05msunsure 🔍
-7% - +1%
-0.15ms - +0.02ms		-

usedJSHeapSize

VersionAvg timevs preact-localvs preact-main
preact-local1.03ms - 1.09ms-unsure 🔍
-5% - +2%
-0.06ms - +0.02ms
preact-main1.05ms - 1.11msunsure 🔍
-2% - +5%
-0.02ms - +0.06ms		-
todo

duration

VersionAvg timevs preact-localvs preact-main
preact-local34.57ms - 35.21ms-unsure 🔍
-2% - +1%
-0.53ms - +0.36ms
preact-main34.66ms - 35.28msunsure 🔍
-1% - +2%
-0.36ms - +0.53ms		-

usedJSHeapSize

VersionAvg timevs preact-localvs preact-main
preact-local1.26ms - 1.26ms-unsure 🔍
+0% - +0%
+0.00ms - +0.00ms
preact-main1.26ms - 1.26msunsure 🔍
-0% - -0%
-0.00ms - -0.00ms		-
update10th1k
  • Browser: chrome-headless
  • Sample size: 160
  • Built by: CI #5567

  • Commit: 5670ac8

duration

VersionAvg timevs preact-localvs preact-main
preact-local25.32ms - 26.68ms-unsure 🔍
-7% - +1%
-1.76ms - +0.33ms
preact-main25.92ms - 27.51msunsure 🔍
-1% - +7%
-0.33ms - +1.76ms		-

usedJSHeapSize

VersionAvg timevs preact-localvs preact-main
preact-local2.99ms - 2.99ms-unsure 🔍
-0% - +0%
-0.01ms - +0.00ms
preact-main2.99ms - 2.99msunsure 🔍
-0% - +0%
-0.00ms - +0.01ms		-

tachometer-reporter-action v2 for CI

@github-actions

github-actions Bot commented Jun 12, 2026 •
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Size Change: +60 B (+0.08%)

Total Size: 79.3 kB

📦 View Changed
Filename Size Change
dist/preact.js 4.8 kB +9 B (+0.19%)
dist/preact.min.js 4.82 kB +9 B (+0.19%)
dist/preact.min.module.js 4.83 kB +8 B (+0.17%)
dist/preact.min.umd.js 4.84 kB +9 B (+0.19%)
dist/preact.mjs 4.83 kB +9 B (+0.19%)
dist/preact.module.js 4.83 kB +9 B (+0.19%)
dist/preact.umd.js 4.85 kB +7 B (+0.14%)
ℹ️ View Unchanged
Filename Size
compat/dist/compat.js 4.19 kB
compat/dist/compat.mjs 4.11 kB
compat/dist/compat.module.js 4.11 kB
compat/dist/compat.umd.js 4.25 kB
debug/dist/debug.js 3.85 kB
debug/dist/debug.mjs 3.85 kB
debug/dist/debug.module.js 3.85 kB
debug/dist/debug.umd.js 3.93 kB
devtools/dist/devtools.js 259 B
devtools/dist/devtools.mjs 274 B
devtools/dist/devtools.module.js 274 B
devtools/dist/devtools.umd.js 345 B
hooks/dist/hooks.js 1.52 kB
hooks/dist/hooks.mjs 1.56 kB
hooks/dist/hooks.module.js 1.56 kB
hooks/dist/hooks.umd.js 1.59 kB
jsx-runtime/dist/jsxRuntime.js 1.01 kB
jsx-runtime/dist/jsxRuntime.mjs 985 B
jsx-runtime/dist/jsxRuntime.module.js 985 B
jsx-runtime/dist/jsxRuntime.umd.js 1.08 kB
test-utils/dist/testUtils.js 473 B
test-utils/dist/testUtils.mjs 477 B
test-utils/dist/testUtils.module.js 477 B
test-utils/dist/testUtils.umd.js 555 B

compressed-size-action

@JoviDeCroock

JoviDeCroock commented Jun 12, 2026 •
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I feel like I've done this before but... time to analyze why replace is degrading this much... Probably hitting GC a lot more...

EDIT: yes removing the _unmount reset of _children did the trick https://github.com/preactjs/preact/compare/c40fd133c1cd7dc452ba1594a763c0776807a01f..5670ac8b8b9222783d2527ebbac88c021995b7b8

@JoviDeCroock
Fix memory leak hotspots
5670ac8 
- render: clear the root Fragment's props.children after commit so replaced vnode generations are not retained

- unmount: clear component._globalContext with the other component references
@JoviDeCroock JoviDeCroock force-pushed the JoviDeCroock/fix-memory-leak-hotspots branch from c40fd13 to 5670ac8 Compare June 13, 2026 04:45
marvinhagemeister
marvinhagemeister approved these changes Jun 14, 2026
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nice find!

@JoviDeCroock JoviDeCroock merged commit bd0302d into v10.x Jun 15, 2026
12 checks passed
@JoviDeCroock JoviDeCroock deleted the JoviDeCroock/fix-memory-leak-hotspots branch June 15, 2026 06:18
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@JoviDeCroock @marvinhagemeister