stream: reduce allocations in StreamBase reads and writes - #64455
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mcollina wants to merge 4 commits into
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stream: reduce allocations in StreamBase reads and writes#64455mcollina wants to merge 4 commits into
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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>
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StreamBase read buffers are now views over a shared 64KB slab (ArrayBuffer plus offset) rather than right-sized copies, so newReadableStreamFromStreamBase must slice nread bytes out of the slab at streamBaseState[kArrayBufferOffset] before enqueueing the chunk, instead of enqueueing the whole slab ArrayBuffer. Fixes test-whatwg-webstreams-adapters-streambase.js failing CI. Signed-off-by: Matteo Collina <hello@matteocollina.com>
jasnell
approved these changes
Aug 15, 2026
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #64455 +/- ##
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- Coverage 90.33% 90.30% -0.03%
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Files 751 751
Lines 250048 250476 +428
Branches 47254 47347 +93
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+ Hits 225877 226193 +316
- Misses 15553 15655 +102
- Partials 8618 8628 +10
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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.