stream: reduce allocations in StreamBase reads and writes by mcollina · Pull Request #64455 · nodejs/node

mcollina · 2026-07-12T15:32:57Z

Read buffers are now allocated from a 64KB slab and handed to JS as views (no per-read allocation, map bookkeeping, or resize copy), and WriteWrap objects are only created when a write does not complete synchronously.

net/net-pipe.js len=1024 type=buf                  +28.4%  (t=22.8)
net/net-c2s.js len=1024 type=buf                   +21.2%  (t=18.0)
net/net-pipe.js len=65536 type=buf                  +4.4%  (t=7.4)
tls/throughput-c2s.js size=16384 type=buf           +2.9%  (t=3.0)
net/tcp-raw-pipe.js, net-s2c, tls s2c              neutral

nodejs-github-bot · 2026-07-12T15:33:02Z

Review requested:

@nodejs/performance

codecov · 2026-08-15T18:44:20Z

Codecov Report

❌ Patch coverage is 77.73109% with 53 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.05%. Comparing base (7aaf9b4) to head (ba6a523).
⚠️ Report is 269 commits behind head on main.

Files with missing lines	Patch %	Lines
src/stream_base.cc	53.24%	24 Missing and 12 partials ⚠️
src/env.cc	80.00%	8 Missing and 5 partials ⚠️
lib/internal/stream_base_commons.js	95.89%	3 Missing ⚠️
src/env.h	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64455      +/-   ##
==========================================
- Coverage   90.13%   90.05%   -0.09%     
==========================================
  Files         751      755       +4     
  Lines      253639   257245    +3606     
  Branches    47790    48761     +971     
==========================================
+ Hits       228618   231654    +3036     
- Misses      16264    16685     +421     
- Partials     8757     8906     +149

Files with missing lines	Coverage Δ
lib/internal/webstreams/adapters.js	`86.72% <100.00%> (+0.11%)`	⬆️
src/stream_base.h	`62.06% <ø> (ø)`
src/stream_wrap.cc	`88.15% <100.00%> (+0.60%)`	⬆️
src/env.h	`97.01% <88.88%> (-1.20%)`	⬇️
lib/internal/stream_base_commons.js	`94.86% <95.89%> (-1.31%)`	⬇️
src/env.cc	`82.19% <80.00%> (-3.16%)`	⬇️
src/stream_base.cc	`76.30% <53.24%> (-3.70%)`	⬇️

... and 111 files with indirect coverage changes

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Read buffers for streams that emit their data to JS were allocated per read: a 64KB backing store, tracked in a map, and then - since reads rarely fill the whole buffer - reallocated to the right size and copied. Allocate read buffers from a 64KB slab instead. Reads reserve the suggested size from the slab and JS receives a view over the slab's ArrayBuffer at the read's offset, using the offset mechanism that onStreamRead already supports. Unused reservation space is rewound when a read returns less than was reserved, so small reads (e.g. TLS records) share a slab. This removes the per-read allocations, the map bookkeeping and the resize copy. Signed-off-by: Matteo Collina <hello@matteocollina.com>

Every stream write created a WriteWrap JS object up front, even though most writes complete synchronously via uv_try_write() and never use it. Let stream_base_commons pass null instead of a request object. StreamBase::Write() already creates the wrap object only when the write does not complete synchronously; return that object to JS (which attaches oncomplete/callback to it) and a plain error code otherwise. Writes that complete synchronously now cross the JS/C++ boundary once and allocate nothing. Callers that pass in a request object (child_process IPC, webstreams adapters) behave as before. Since Http2Stream::DoWrite() can invoke the completion callback synchronously - before JS has attached oncomplete - such completions are now recorded on the request object's writeStatus field and replayed by stream_base_commons after dispatch. This also replaces a Has() plus name-based MakeCallback() pair with a single Get(). Also pre-create the JS fields of WriteWrap instances in the object template, as was already done for ShutdownWrap, so that they are in-object properties. Signed-off-by: Matteo Collina <hello@matteocollina.com>

nodejs-github-bot · 2026-09-07T06:47:01Z

CI: https://ci.nodejs.org/job/node-test-pull-request/77122/

nodejs-github-bot · 2026-09-07T14:49:14Z

Landed in a701540...b113d09

Read buffers for streams that emit their data to JS were allocated per read: a 64KB backing store, tracked in a map, and then - since reads rarely fill the whole buffer - reallocated to the right size and copied. Allocate read buffers from a 64KB slab instead. Reads reserve the suggested size from the slab and JS receives a view over the slab's ArrayBuffer at the read's offset, using the offset mechanism that onStreamRead already supports. Unused reservation space is rewound when a read returns less than was reserved, so small reads (e.g. TLS records) share a slab. This removes the per-read allocations, the map bookkeeping and the resize copy. Signed-off-by: Matteo Collina <hello@matteocollina.com> PR-URL: #64455 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Robert Nagy <ronagy@icloud.com>

Every stream write created a WriteWrap JS object up front, even though most writes complete synchronously via uv_try_write() and never use it. Let stream_base_commons pass null instead of a request object. StreamBase::Write() already creates the wrap object only when the write does not complete synchronously; return that object to JS (which attaches oncomplete/callback to it) and a plain error code otherwise. Writes that complete synchronously now cross the JS/C++ boundary once and allocate nothing. Callers that pass in a request object (child_process IPC, webstreams adapters) behave as before. Since Http2Stream::DoWrite() can invoke the completion callback synchronously - before JS has attached oncomplete - such completions are now recorded on the request object's writeStatus field and replayed by stream_base_commons after dispatch. This also replaces a Has() plus name-based MakeCallback() pair with a single Get(). Also pre-create the JS fields of WriteWrap instances in the object template, as was already done for ShutdownWrap, so that they are in-object properties. Signed-off-by: Matteo Collina <hello@matteocollina.com> PR-URL: #64455 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Robert Nagy <ronagy@icloud.com>

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs involving general changes in the lib/ or src/ directories. needs-ci PRs that need a full CI run. labels Jul 12, 2026

mcollina force-pushed the streambase-perf branch from 46c68b3 to 6a68f9e Compare July 12, 2026 15:52

GetThatCookie mentioned this pull request Aug 3, 2026

http,net,stream: reconcile read, write, and parser paths #64980

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jasnell approved these changes Aug 15, 2026

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mcollina force-pushed the streambase-perf branch from 91250fb to e4043cd Compare September 2, 2026 05:45

mcollina added 2 commits September 2, 2026 09:37

mcollina force-pushed the streambase-perf branch from e4043cd to ba6a523 Compare September 2, 2026 07:37

ronag approved these changes Sep 7, 2026

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stream: reduce allocations in StreamBase reads and writes - #64455

stream: reduce allocations in StreamBase reads and writes#64455
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