buffer: speed up concat via TypedArray#set #60399

gurgunday · 2025-10-25T00:47:41Z

Huge win by avoiding complex _copyActual logic when we can copy the whole source into target. The native copy implementation is faster only for partial copies.

Before:

buffers/buffer-concat-fill.js
buffers/buffer-concat-fill.js n=800000 extraSize=1: 3,080,309.438799309
buffers/buffer-concat-fill.js n=800000 extraSize=256: 2,718,494.3906977526
buffers/buffer-concat-fill.js n=800000 extraSize=1024: 2,592,930.9112553936

buffers/buffer-concat.js
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=1 pieces=4: 6,895,296.007515873
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=1 pieces=4: 6,850,915.824861098
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=16 pieces=4: 6,714,498.121438699
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=16 pieces=4: 6,606,244.795672606
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=256 pieces=4: 3,875,370.506613865
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=256 pieces=4: 4,427,107.007979794
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=1 pieces=16: 2,202,621.1880456866
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=1 pieces=16: 2,308,511.109946339
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=16 pieces=16: 2,111,185.355049204
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=16 pieces=16: 2,169,882.104202485
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=256 pieces=16: 993,752.7633158871
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=256 pieces=16: 1,010,066.0454915363

After:

buffers/buffer-concat-fill.js
buffers/buffer-concat-fill.js n=800000 extraSize=1: 4,213,313.932988885
buffers/buffer-concat-fill.js n=800000 extraSize=256: 3,999,625.0351529545
buffers/buffer-concat-fill.js n=800000 extraSize=1024: 3,271,098.409944823

buffers/buffer-concat.js
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=1 pieces=4: 12,018,365.504695036
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=1 pieces=4: 11,561,090.427597769
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=16 pieces=4: 11,106,682.475733392
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=16 pieces=4: 10,827,423.883277772
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=256 pieces=4: 6,297,132.164792359
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=256 pieces=4: 6,326,826.005617953
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=1 pieces=16: 4,151,263.382265607
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=1 pieces=16: 4,295,939.1963506
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=16 pieces=16: 3,758,688.301977228
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=16 pieces=16: 3,904,910.547041359
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=256 pieces=16: 1,265,188.4389452678
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=256 pieces=16: 1,284,207.4931866652

lib/buffer.js

codecov · 2025-10-25T01:50:19Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.56%. Comparing base (2bda7cb) to head (a8a5e19).
⚠️ Report is 59 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60399      +/-   ##
==========================================
- Coverage   88.56%   88.56%   -0.01%     
==========================================
  Files         704      704              
  Lines      207774   207832      +58     
  Branches    40025    40048      +23     
==========================================
+ Hits       184022   184066      +44     
+ Misses      15807    15806       -1     
- Partials     7945     7960      +15

Files with missing lines	Coverage Δ
lib/buffer.js	`100.00% <100.00%> (ø)`

... and 49 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

mcollina

lgtm

aduh95 · 2025-10-25T19:21:04Z

Benchmark GHA: https://github.com/aduh95/node/actions/runs/18809427089
Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1746/

Results (improvements across the board)

336.392                                                                              confidence improvement accuracy (*)   (**)  (***)
336.392  buffers/buffer-concat-fill.js n=800000 extraSize=1                                 ***     18.19 %       ±1.07% ±1.42% ±1.85%
336.392  buffers/buffer-concat-fill.js n=800000 extraSize=1024                              ***     12.89 %       ±0.87% ±1.16% ±1.51%
336.392  buffers/buffer-concat-fill.js n=800000 extraSize=256                               ***     16.73 %       ±0.87% ±1.16% ±1.51%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=1 pieces=16          ***    100.26 %       ±1.68% ±2.26% ±2.99%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=1 pieces=4           ***     56.72 %       ±2.03% ±2.72% ±3.60%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=16 pieces=16         ***     96.79 %       ±1.62% ±2.17% ±2.87%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=16 pieces=4          ***     60.41 %       ±2.24% ±3.00% ±3.93%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=256 pieces=16        ***     12.61 %       ±0.53% ±0.71% ±0.93%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=256 pieces=4         ***     23.27 %       ±1.02% ±1.36% ±1.77%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=1 pieces=16          ***     98.73 %       ±1.27% ±1.71% ±2.26%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=1 pieces=4           ***     57.20 %       ±2.52% ±3.36% ±4.41%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=16 pieces=16         ***     96.40 %       ±1.37% ±1.85% ±2.44%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=16 pieces=4          ***     57.44 %       ±2.48% ±3.32% ±4.36%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=256 pieces=16        ***     11.19 %       ±0.61% ±0.81% ±1.07%
336.392  buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=256 pieces=4         ***     21.48 %       ±1.03% ±1.38% ±1.80%

                                                                            confidence improvement accuracy (*)    (**)   (***)
buffers/buffer-concat-fill.js n=800000 extraSize=1                                 ***     82.25 %      ±16.94% ±22.34% ±28.67%
buffers/buffer-concat-fill.js n=800000 extraSize=1024                              ***     49.50 %      ±11.42% ±15.05% ±19.31%
buffers/buffer-concat-fill.js n=800000 extraSize=256                               ***     71.99 %      ±15.96% ±21.05% ±27.01%
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=1 pieces=16          ***    230.61 %      ±19.95% ±26.30% ±33.75%
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=1 pieces=4           ***    182.24 %      ±18.07% ±23.82% ±30.57%
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=16 pieces=16         ***    218.33 %      ±19.78% ±26.07% ±33.45%
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=16 pieces=4          ***    171.75 %      ±18.22% ±24.02% ±30.83%
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=256 pieces=16        ***     52.84 %      ±20.58% ±27.13% ±34.82%
buffers/buffer-concat.js n=800000 withTotalLength=0 pieceSize=256 pieces=4         ***     87.04 %      ±17.05% ±22.47% ±28.84%
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=1 pieces=16          ***    234.11 %      ±20.43% ±26.94% ±34.57%
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=1 pieces=4           ***    174.42 %      ±18.13% ±23.89% ±30.66%
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=16 pieces=16         ***    220.85 %      ±20.02% ±26.39% ±33.87%
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=16 pieces=4          ***    166.60 %      ±17.70% ±23.33% ±29.94%
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=256 pieces=16        ***     52.35 %      ±20.66% ±27.24% ±34.96%
buffers/buffer-concat.js n=800000 withTotalLength=1 pieceSize=256 pieces=4         ***     87.00 %      ±17.03% ±22.46% ±28.82%

Be aware that when doing many comparisons the risk of a false-positive
result increases. In this case, there are 15 comparisons, you can thus
expect the following amount of false-positive results:
  0.75 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.15 false positives, when considering a   1% risk acceptance (**, ***),
  0.01 false positives, when considering a 0.1% risk acceptance (***)

gurgunday · 2025-10-25T20:57:04Z

@aduh95 the CI didn't pick up the benchmarks, I think the category is buffers instead of buffer

lib/buffer.js

This reverts commit 34adb7c.

gurgunday · 2025-10-26T20:41:10Z

No, they claimed an improvement for copy, which works with TypedArrays.

However, .concat, which only works with UInt8 arrays, did get slower because of this. Because it's now using a more complex logic as well while not needing it.

source = new Uint8Array(source.buffer, source.byteOffset + sourceStart, nb);

Funnily enough, we weren't using primordials here before, but anyway, that change is already made

Co-authored-by: Nikita Skovoroda <chalkerx@gmail.com>

gurgunday · 2025-10-26T21:33:46Z

We might need a CI run to verify

lib/buffer.js

richardlau · 2025-10-28T22:07:31Z

The AIX and LinuxOne CI failures look like real issues with this PR and is most likely due to not handling endianness properly.

gurgunday · 2025-10-29T07:50:20Z

Yeah my fault it's the test, will fix it later today

gurgunday · 2025-10-29T22:36:04Z

@richardlau thanks, should be fixed

@aduh95 PTAL, it's ready for review again

gurgunday · 2025-10-31T09:50:15Z

@lpinca PTAL

Ignore the mountain of comments, here are the results, it's non-breaking

You can run the bench again but it's ready with a request-ci

nodejs-github-bot · 2025-10-31T20:06:14Z

Commit Queue failed

- Loading data for nodejs/node/pull/60399
✔  Done loading data for nodejs/node/pull/60399
----------------------------------- PR info ------------------------------------
Title      buffer: speed up concat via TypedArray#set (#60399)
   ⚠  Could not retrieve the email or name of the PR author's from user's GitHub profile!
Branch     gurgunday:buffer-concat -> nodejs:main
Labels     buffer, performance, author ready, needs-ci, commit-queue-squash
Commits    10
 - buffer: speed up concat via TypedArray#set
 - complete coverage
 - store bufLength in a variable
 - fix compat issue
 - lint
 - simplify
 - Revert "simplify"
 - alternative implementation
 - add type check to set
 - fix test
Committers 1
 - Gürgün Dayıoğlu <hey@gurgun.day>
PR-URL: https://github.com/nodejs/node/pull/60399
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/60399
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
--------------------------------------------------------------------------------
   ℹ  This PR was created on Sat, 25 Oct 2025 00:47:41 GMT
   ✔  Approvals: 3
   ✔  - Matteo Collina (@mcollina) (TSC): https://github.com/nodejs/node/pull/60399#pullrequestreview-3380174635
   ✔  - Antoine du Hamel (@aduh95) (TSC): https://github.com/nodejs/node/pull/60399#pullrequestreview-3380355020
   ✔  - Rafael Gonzaga (@RafaelGSS) (TSC): https://github.com/nodejs/node/pull/60399#pullrequestreview-3405890961
   ✔  Last GitHub CI successful
   ℹ  Last Benchmark CI on 2025-10-27T22:47:38Z: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1748/
   ℹ  Last Full PR CI on 2025-10-27T23:11:11Z: https://ci.nodejs.org/job/node-test-pull-request/69912/
   ⚠  Commits were pushed after the last Full PR CI run:
   ⚠  - fix test
- Querying data for job/node-test-pull-request/69912/
   ✔  Last Jenkins CI successful
--------------------------------------------------------------------------------
   ✔  Aborted `git node land` session in /home/runner/work/node/node/.ncu

https://github.com/nodejs/node/actions/runs/18983880877

gurgunday · 2025-10-31T20:07:48Z

@aduh95 it needs a CI run after the test fix

nodejs-github-bot · 2025-10-31T22:22:19Z

CI: https://ci.nodejs.org/job/node-test-pull-request/69979/

nodejs-github-bot · 2025-11-01T22:51:57Z

Landed in 24bebd0

PR-URL: #60399 Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

buffer: speed up concat via TypedArray#set

e10034f

nodejs-github-bot added buffer Issues and PRs related to the buffer subsystem. needs-ci PRs that need a full CI run. labels Oct 25, 2025

gurgunday added the performance Issues and PRs related to the performance of Node.js. label Oct 25, 2025

ChALkeR reviewed Oct 25, 2025

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