[davidfowl]

HttpParser.TryParseRequestLine finds the end of the query string with a scalar byte-by-byte loop that looks for the space before the HTTP version. This PR replaces that loop with ReadOnlySpan<byte>.IndexOf(ByteSpace), which is vectorized. The resulting offset is identical: the index of the first space, or requestLine.Length if there is none. The path portion before it already uses IndexOfAny.

Benchmarks

Local BenchmarkDotNet (InProcess, MemoryDiagnoser), 2 vCPU VM, 4 interleaved base/PR rounds. Two benchmarks are new in HttpParserBenchmark:

• QueryString: /api/products/search?q=...&page=2&pageSize=24, a 121-byte query
• ShortQueryString: /api/items?id=42

Benchmark	main (rounds)	PR (rounds)	Δ
QueryString	85.6 / 88.2 / 89.6 / 87.2 ns	54.4 / 56.1 / 55.6 / 54.9 ns	-37%
ShortQueryString	50.4 / 49.1 / 48.7 / 53.1 ns	50.3 / 50.5 / 50.6 / 53.0 ns	noise

Existing HttpParserBenchmark cases (PlaintextTechEmpower, JsonTechEmpower, LiveAspNet, Unicode, MultispanUnicodeHeader) have no query string and are unchanged within noise over 3 rounds. No allocations in any case.

Tests

Microsoft.AspNetCore.Server.Kestrel.Core.Tests filtered to HttpParserTests, Http1ConnectionTests, StartLine, HttpRequestLine and Target: 7194 passed, 0 failed.

No API / behavior change

• Internal implementation only. No PublicAPI.*.txt changes and no new APIs.
• Parsed path, query and error behavior are identical.

🤖 Posted by ASP.NET Core Perf 2 (AI Agent)

[Copilot]

🔵 Needs a closer look

The frozen review bundle, prior feedback, and independent guide reviews were unavailable, preventing completion of the required review process and verification of revision provenance.

No open issues 🎉

What changed in this PR

Optimizes Kestrel’s HTTP/1.1 request-line parsing by replacing the scalar query-string terminator search with a vectorized span search, preserving the resulting offset.

Changes:

• Uses ReadOnlySpan<byte>.IndexOf(ByteSpace) to locate the query’s ending space.
• Adds long- and short-query benchmarks to measure performance.

File	Description
src/​Servers/​Kestrel/​perf/​Microbenchmarks/​HttpParserBenchmark.cs	Adds long- and short-query request parsing benchmarks.
src/​Servers/​Kestrel/​Core/​src/​Internal/​Http/​HttpParser.cs	Replaces the query scan loop with IndexOf, retaining the no-space fallback.

_{Review effort: Balanced}

[davidfowl]

Pushed an empty commit to retrigger CI. Both failures look unrelated to this change, which only affects how the HTTP/1.1 request-line parser finds the end of the query string:

• Http2ConnectionTests.GOAWAY_Received_ConnectionLifetimeNotification_Cancelled (Ubuntu 24.04, line 4493): HTTP/2 doesn't use the HTTP/1.1 request-line parser. This test was previously quarantined as flaky (Quarantine Http2ConnectionTests (AbortedStream_ResetsAndDrainsRequest_RefusesFramesAfterEndOfStream, StopProcessingNextRequestSendsGracefulGOAWAYThenFinalGOAWAYWhenAllStreamsComplete, AbortSendsFinalGOAWAY, GOAWAY_Received_ConnectionLifetimeNotification_Cancelled) #66037) and later unquarantined ([test-quarantine] Unquarantine 3 Http2ConnectionTests (issue #66037) #66491). It passed 15 of 15 runs locally on this branch.
• VirtualizationTest.VariableHeight_HtmlTable_DoesNotProduceNestedTrElements (Blazor E2E): it also fails intermittently on unrelated PRs ([main] Source code updates from dotnet/dotnet #70108, and Use ulong.TryFormat for Content-Length values >= 1000 in Kestrel #70136's first run), and a sibling VirtualizationTest is quarantined (Quarantine Microsoft.AspNetCore.Components.E2ETest.Tests.VirtualizationTest.InitialIndex_PendingGrowth_TallItemsBeforeTarget_Kee [Content t #69093).

🤖 Posted by ASP.NET Core Perf 2 (AI Agent)

[davidfowl]

On the retriggered run, aspnetcore-ci (build plus all Helix tests) is green, including the Http2 GOAWAY test. The only failure was Blazor E2E (Mono server): ServerVirtualizationTest.CancelsOutdatedRefreshes_Async. That test has a long flakiness history: it was quarantined in #66120/#66123, re-quarantined in #68016, and stabilization was attempted in #68079 and #32869. It's unrelated to Kestrel's HTTP/1.1 request-line parsing, so I pushed another empty commit to retrigger.

🤖 Posted by ASP.NET Core Perf 2 (AI Agent)

[PureWeen]

/review