stream: fold desired-size check into WHATWG backpressure update#64451
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mcollina wants to merge 2 commits into
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stream: fold desired-size check into WHATWG backpressure update#64451mcollina wants to merge 2 commits into
mcollina wants to merge 2 commits into
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The [[queue]] backing the controllers became a ring buffer, but the read and write request queues (readRequests, readIntoRequests, writeRequests) were left as plain arrays consumed with ArrayPrototypeShift, which is O(n) and, even for the single pending request of the await-each regime, far slower than an indexed head advance. Back them with the same Queue, materialized lazily from the shared empty queue so acquiring a reader or constructing a writer allocates no request storage until a read or write actually parks. pipe-to: +4.7% to +9.4% (all 16 configs, ***) readable-read type=byob: +2.3% (**) parked read loop: +15%, write loop: +11% (local harness) Follow-up to nodejs#64312. Signed-off-by: Matteo Collina <hello@matteocollina.com>
writableStreamUpdateBackpressure ran two release-mode assertions and took a precomputed backpressure value that every caller derived with a separate GetBackpressure/GetDesiredSize call pair. All callers already hold the 'writable', not-close-queued invariant the assertions checked, so derive the backpressure from the desired size inside the function and drop the assertions and the helper. This runs up to twice per write. writer.write() loop: +10%, pipe-to: +4.6% avg over 16 configs (local harness / benchmark, all configs positive). Signed-off-by: Matteo Collina <hello@matteocollina.com>
jasnell
approved these changes
Jul 12, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #64451 +/- ##
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- Coverage 90.24% 90.24% -0.01%
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Files 741 741
Lines 241384 241610 +226
Branches 45480 45519 +39
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+ Hits 217844 218041 +197
- Misses 15097 15110 +13
- Partials 8443 8459 +16
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writableStreamUpdateBackpressureran two release-mode assertions and took a precomputed backpressure value that every caller derived with a separateGetBackpressure/GetDesiredSizecall pair. All callers already hold thewritable, not-close-queued invariant the assertions checked, so the backpressure is now derived from the desired size inside the function, dropping the assertions and the helper. This runs up to twice per write.The first commit is #64431; only the last commit is new here.