stream: speed up reads and iteration over default WHATWG streams#64320
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mcollina wants to merge 3 commits into
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stream: speed up reads and iteration over default WHATWG streams#64320mcollina wants to merge 3 commits into
mcollina wants to merge 3 commits into
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for await / reader.read() loops over byte streams were ~4x slower than over default streams. Three per-chunk costs, none required by the spec: - ArrayBufferViewGetBuffer/ByteLength/ByteOffset went through ReflectGet(view.constructor.prototype, ...), a reflective get that is ~3.5x slower than the original prototype getters from primordials and spoofable through a user-defined .constructor to boot. - The buffered fast paths in ReadableStreamDefaultReader.read() and the async iterator only covered default controllers, so byte streams with queued data still allocated a read request and PromiseWithResolvers per chunk. Byte-queue dequeue is fully synchronous (it is the queue-filled arm of the byte controller's pull steps), so both fast paths now resolve directly from the byte queue. - readableByteStreamControllerEnqueue re-ran the reader brand check and re-loaded the read request list four times per chunk across HasDefaultReader / ProcessReadRequestsUsingQueue / GetNumReadRequests / FulfillReadRequest; it now does a single pass. The async iterator also reuses its read request object across reads (at most one is ever in flight). benchmark/webstreams interleaved same-day A/B, --runs 10: readable-async-iterator bytes +16.3% (***), readable-read byob +9.1% (***), all other rows neutral. Profiler harness: parked byte iteration +14%, buffered byte iteration +37%, buffered byte read loop +18%, default-stream rows at parity. WPT streams/compression/encoding subtests identical to baseline. Signed-off-by: Matteo Collina <hello@matteocollina.com>
Signed-off-by: Matteo Collina <hello@matteocollina.com>
Skip the size algorithm call and its result validation when the size algorithm is the default one, and stop re-running the full ShouldCallPull predicate at per-chunk call sites where its inputs are already established. readable-async-iterator type=normal: +16.6% (***) readable-read-buffered: +13.9% to +27.5% (**/***) pipe-to: +3.7% to +6.0% (15/16 configs significant) Signed-off-by: Matteo Collina <hello@matteocollina.com>
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Skip the size algorithm call when it is the default one, and stop re-running the full ShouldCallPull predicate at per-chunk call sites where its inputs are already established.
The first two commits are #64291; only the last commit is new here.