.NET 10 vs main (Mid-July data) Wasm Mono AOT Performance Regression Tracking issue

# [.NET 10 vs main] WASM-Mono-AOT performance regression tracking

This issue tracks the actionable `WASM-Mono-AOT` results from the reviewed release/10.0 vs main windowed comparison. Draft generated **2026-08-17**. GitHub issue/PR states refreshed from live metadata on **2026-08-17**. User decisions and AI-attributed notes applied on **2026-08-17**.

Use the checkboxes in place: leave an item unchecked while investigation, filing, ownership, or verification remains; check it when that work is finished. Feel free to edit or append status directly on the same checklist line as work progresses. There is intentionally no separate Completed section.

Within each section, items are ordered by worst reviewed percentage (largest first). Regression count is used only to break ties.

### Inclusion rules

Included: `needs-investigation`, confirmed runtime regressions, unmarked runtime/autofiling/missed items, and missed regressions marked `truly-missed`.

Excluded: `fixed`, `acceptable`, `not-applicable`, `noise`, `improved`, `baseline-outlier`, `covered`, and `linked`.

### Actionable summary

| Area | Items |
| --- | ---: |
| Needs investigation (runtime + ungrouped missed) | 2 |
| Active tracked runtime regressions | 0 |
| Autofiling issues needing transfer/resolution | 22 |
| Missed regression date groups needing filing | 3 |
| **Total checkboxes** | **27** |

## Needs investigation

Show 2 items

Items requiring a second look before deciding whether to file, transfer, accept, or close them.

- [ ] [dotnet/runtime#129860](https://github.com/dotnet/runtime/issues/129860) — **needs-investigation**; `open`; 72 `WASM-Mono-AOT` reviewed regressions; worst +85.3%; regression date 2026-06-24. **Review note:** Need to double check it stays, but it seems fixed. (as stated in https://github.com/dotnet/runtime/issues/129860#issuecomment-5028570718) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Text.Json.Tests.Perf_Reader.ReadSpanEmptyLoop%28IsDataCompact%3A%20False%2C%20TestCase%3A%20BroadTree%29.html).

- [ ] [dotnet/runtime#126361](https://github.com/dotnet/runtime/issues/126361) — **needs-investigation**; `closed-not-planned`; 13 `WASM-Mono-AOT` reviewed regressions; worst +50.7%; regression date 2026-03-27. **Review note:** Marked acceptable as the impacts on CoreCLR were small. Still needs a Wasm-Mono-AOT look over. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Numerics.Tests.Perf_BigInteger.Add%28arguments%3A%201024%2C1024%20bits%29.html).

## Active tracked regressions

_No items selected by the current inclusion rules._

## Autofiling issues needing transfer or resolution

Show 22 items

Uncorrelated autofiling issues that are unmarked or marked `needs-investigation`.

- [ ] [dotnet/perf-autofiling-issues#73330](https://github.com/dotnet/perf-autofiling-issues/issues/73330) — **needs-investigation**; `open`; 18 `WASM-Mono-AOT` reviewed regressions; worst +111.1%; regression date 2026-05-19. **Review note:** Probably due to BDN update https://github.com/dotnet/perf-autofiling-issues/issues/73304, still seeing regressions so marking needs-investigation. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Linq.Tests.Perf_ImmutableArrayExtensions.SequenceEqual%28input%3A%20ICollection%29.html).

- [ ] [dotnet/perf-autofiling-issues#62589](https://github.com/dotnet/perf-autofiling-issues/issues/62589) — **needs-investigation**; `open`; 219 `WASM-Mono-AOT` reviewed regressions; worst +109.1%; regression date 2025-09-09. **Review note:** Some still are regressed from this regression: such as System.Globalization.Tests.StringSearch.IsSuffix_SecondHalf(Options: (pl-PL, None, False)) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Tests.Perf_Uri.CtorIdnHostPathAndQuery%28input%3A%20%22http%3A//host/%22%29.html).

- [ ] [dotnet/perf-autofiling-issues#64552](https://github.com/dotnet/perf-autofiling-issues/issues/64552) — **needs-investigation**; `open`; 19 `WASM-Mono-AOT` reviewed regressions; worst +109.1%; regression date 2025-10-27. **Review note:** Initial look, but no follow-up or closeout. AI Note: PR #121096 is a potential culprit and warrants targeted follow-up. ([evidence](https://github.com/dotnet/perf-autofiling-issues/issues/64552#issuecomment-5110150799)) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Tests.Perf_Uri.CtorIdnHostPathAndQuery%28input%3A%20%22http%3A//host/%22%29.html).

- [ ] [dotnet/perf-autofiling-issues#75372](https://github.com/dotnet/perf-autofiling-issues/issues/75372) — **needs-investigation**; `open`; 12 `WASM-Mono-AOT` reviewed regressions; worst +109.1%; regression date 2026-06-25. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Tests.Perf_Uri.CtorIdnHostPathAndQuery%28input%3A%20%22http%3A//host/%22%29.html).

- [ ] [dotnet/perf-autofiling-issues#76345](https://github.com/dotnet/perf-autofiling-issues/issues/76345) — **needs-investigation**; `open`; 1 `WASM-Mono-AOT` reviewed regressions; worst +67.9%; regression date 2026-07-13. **Review note:** AI Note: A real two-step WASM-AOT regression is documented; bisection remains deferred. ([evidence](https://github.com/dotnet/perf-autofiling-issues/issues/76345#issuecomment-4991556016)) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Buffers.Text.Tests.Utf8ParserTests.TryParseDecimal%28value%3A%20123456.789%29.html).

- [ ] [dotnet/perf-autofiling-issues#75373](https://github.com/dotnet/perf-autofiling-issues/issues/75373) — **needs-investigation**; `open`; 47 `WASM-Mono-AOT` reviewed regressions; worst +63.6%; regression date 2026-06-25. **Review note:** https://github.com/dotnet/runtime/pull/129299 was linked as the likely cause, but no specific ok/acceptable has been given. Some regressions have unregressed. AI Note: Sibling issue #75780 was attributed to the same change; toolchain-upgrade disposition remains unresolved. ([evidence](https://github.com/dotnet/perf-autofiling-issues/issues/75373#issuecomment-5228270726)) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/Struct.GSeq.FilterSkipMapSum.html).

- [ ] [dotnet/perf-autofiling-issues#70611](https://github.com/dotnet/perf-autofiling-issues/issues/70611) — **needs-investigation**; `open`; 2 `WASM-Mono-AOT` reviewed regressions; worst +48.3%; regression date 2026-03-19. **Review note:** No updates since initial look basically (march) AI Note: A July 28 re-examination reconfirmed the Regex and MemorySpan regressions. ([evidence](https://github.com/dotnet/perf-autofiling-issues/issues/70611#issuecomment-5110295650)) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Memory.Span%28Char%29.Reverse%28Size%3A%20512%29.html).

- [ ] [dotnet/perf-autofiling-issues#65460](https://github.com/dotnet/perf-autofiling-issues/issues/65460) — **needs-investigation**; `closed-completed`; 2 `WASM-Mono-AOT` reviewed regressions; worst +40.8%; regression date 2025-11-21. **Review note:** These still seem like real regression (both) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Buffers.Tests.NonStandardArrayPoolTests%28Byte%29.RentNoReturn%28RentalSize%3A%2064%2C%20UseSharedPool%3A%20True%29.html).

- [ ] [dotnet/perf-autofiling-issues#76183](https://github.com/dotnet/perf-autofiling-issues/issues/76183) — **needs-investigation**; `open`; 6 `WASM-Mono-AOT` reviewed regressions; worst +37.4%; regression date 2026-07-10. **Review note:** Large gap and still real. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Text.Json.Tests.Perf_Booleans.WriteBooleans%28Formatted%3A%20False%2C%20SkipValidation%3A%20True%29.html).

- [ ] [dotnet/perf-autofiling-issues#75371](https://github.com/dotnet/perf-autofiling-issues/issues/75371) — **needs-investigation**; `open`; 2 `WASM-Mono-AOT` reviewed regressions; worst +37.0%; regression date 2026-06-25. **Review note:** Real and still valid, no obvious runtime issue yet. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Net.Primitives.Tests.CredentialCacheTests.GetCredential_Uri%28uriString%3A%20%22http%3A//name5%22%2C%20uriCount%3A%2010%29.html).

- [ ] [dotnet/perf-autofiling-issues#64174](https://github.com/dotnet/perf-autofiling-issues/issues/64174) — **needs-investigation**; `open`; 11 `WASM-Mono-AOT` reviewed regressions; worst +31.5%; regression date 2025-10-17. **Review note:** Due to partial revert https://github.com/dotnet/runtime/pull/120742, seems some reverted to worse than before (System.Globalization.Tests.StringSearch). [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Globalization.Tests.StringSearch.IsPrefix_FirstHalf%28Options%3A%20%28pl-PL%2C%20None%2C%20False%29%29.html).

- [x] [dotnet/perf-autofiling-issues#76544](https://github.com/dotnet/perf-autofiling-issues/issues/76544) — **noise**; `open`; 8 `WASM-Mono-AOT` reviewed regressions; worst +31.5%; regression date 2026-07-13. **Review note:** User update: Closed as Noise. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Globalization.Tests.StringSearch.IsPrefix_FirstHalf%28Options%3A%20%28pl-PL%2C%20None%2C%20False%29%29.html).

- [ ] [dotnet/perf-autofiling-issues#73326](https://github.com/dotnet/perf-autofiling-issues/issues/73326) — **needs-investigation**; `open`; 2 `WASM-Mono-AOT` reviewed regressions; worst +27.2%; regression date 2026-05-15. **Review note:** System.Collections.Sort<IntClass>.List(Size: 512) is regressed from this but the test on the issue is improved. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Collections.Sort%28IntClass%29.List%28Size%3A%20512%29.html).

- [ ] [dotnet/perf-autofiling-issues#73166](https://github.com/dotnet/perf-autofiling-issues/issues/73166) — **needs-investigation**; `open`; 1 `WASM-Mono-AOT` reviewed regressions; worst +21.3%; regression date 2026-05-13. **Review note:** This still seems to be regressed. (Though date is slightly off). [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Buffers.Binary.Tests.BinaryReadAndWriteTests.ReadStructFieldByFieldUsingBitConverterBE.html).

- [ ] [dotnet/perf-autofiling-issues#73724](https://github.com/dotnet/perf-autofiling-issues/issues/73724) — **needs-investigation**; `open`; 1 `WASM-Mono-AOT` reviewed regressions; worst +17.6%; regression date 2026-05-21. **Review note:** Seems like it improved and then regressed again, but we only had 1 good run after the improvements. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Tests.Perf_Uri.EscapeDataString%28input%3A%20%22%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%7B%22%29.html).

- [ ] [dotnet/perf-autofiling-issues#71720](https://github.com/dotnet/perf-autofiling-issues/issues/71720) — **needs-investigation**; `open`; 4 `WASM-Mono-AOT` reviewed regressions; worst +16.8%; regression date 2026-04-14. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.IO.Hashing.Tests.Crc64_AppendPerf.Append%28BufferSize%3A%2016%29.html).

- [ ] [dotnet/perf-autofiling-issues#62762](https://github.com/dotnet/perf-autofiling-issues/issues/62762) — **needs-investigation**; `open`; 1 `WASM-Mono-AOT` reviewed regressions; worst +15.5%; regression date 2025-09-18. **Review note:** Seems to be real and uninvestigated. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Numerics.Tests.Perf_BigInteger.ToStringX%28numberString%3A%2012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890%29.html).

- [ ] [dotnet/perf-autofiling-issues#73325](https://github.com/dotnet/perf-autofiling-issues/issues/73325) — **needs-investigation**; `open`; 4 `WASM-Mono-AOT` reviewed regressions; worst +15.4%; regression date 2026-05-14. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Numerics.Tests.Perf_BigInteger.ToStringD%28numberString%3A%20-2147483648%29.html).

- [ ] [dotnet/perf-autofiling-issues#61031](https://github.com/dotnet/perf-autofiling-issues/issues/61031) — **needs-investigation**; `open`; 1 `WASM-Mono-AOT` reviewed regressions; worst +14.1%; regression date 2025-08-16. **Review note:** Linked to a PR but still real. Maybe before the branching of release 10 as the net10 baseline is post this it seems. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Linq.Tests.Perf_Enumerable.EmptyTakeSelectToArray.html).

- [ ] [dotnet/perf-autofiling-issues#73163](https://github.com/dotnet/perf-autofiling-issues/issues/73163) — **needs-investigation**; `open`; 3 `WASM-Mono-AOT` reviewed regressions; worst +13.6%; regression date 2026-05-13. **Review note:** System.Collections.IterateForEach<String>.HashSet(Size: 512) seems to still be affected. (Among other regressions at the time from the issue. AI Note: The issue was closed and immediately reopened, indicating the regression remains active. ([evidence](https://github.com/dotnet/perf-autofiling-issues/issues/73163)) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Collections.IterateForEach%28String%29.HashSet%28Size%3A%20512%29.html).

- [ ] [dotnet/perf-autofiling-issues#61032](https://github.com/dotnet/perf-autofiling-issues/issues/61032) — **needs-investigation**; `open`; 3 `WASM-Mono-AOT` reviewed regressions; worst +12.6%; regression date 2025-08-17. [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.MathBenchmarks.Single.Exp10M1.html).

- [x] [dotnet/perf-autofiling-issues#73170](https://github.com/dotnet/perf-autofiling-issues/issues/73170) — **linked**; `closed-completed`; 4 `WASM-Mono-AOT` reviewed regressions; worst +11.1%; regression date 2026-05-14. **Review note:** All 4 of these are still real and regressed from this date. AI Note (user-approved): Closed as a triage redirect and linked to perf-autofiling-issues#73325; this is not proof the regression was fixed. ([evidence](https://github.com/dotnet/perf-autofiling-issues/issues/73170#issuecomment-5110462135)) [Representative chart](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Collections.IterateForEach%28String%29.Queue%28Size%3A%20512%29.html).

## Missed regression groups needing filing

Show 3 items

Dated groups containing at least one `needs-investigation` or `truly-missed` regression. The checkbox represents the group as one candidate public tracking issue.

- [ ] **Regression group 2026-03-26** — 7 actionable of 7 related regressions; worst +20.0%; queues `Ubuntu-x64-Viper`. **Review notes:** Specific tiem is March 26th, 15:05 on the graph
- Potential existing issues within ±7 days: [dotnet/perf-autofiling-issues#70477](https://github.com/dotnet/perf-autofiling-issues/issues/70477), [dotnet/perf-autofiling-issues#70611](https://github.com/dotnet/perf-autofiling-issues/issues/70611), [dotnet/perf-autofiling-issues#70614](https://github.com/dotnet/perf-autofiling-issues/issues/70614)
- [`System.Memory.Slice.MemoryStartLengthSpan`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Memory.Slice%28Byte%29.MemoryStartLengthSpan.html) — `Ubuntu-x64-Viper`; +20.0%; 5.71 → 6.85; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- [`System.Memory.Slice.ReadOnlyMemoryStartLengthSpan`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Memory.Slice%28Byte%29.ReadOnlyMemoryStartLengthSpan.html) — `Ubuntu-x64-Viper`; +18.0%; 5.69 → 6.72; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- [`Benchstone.BenchF.Whetsto.Test`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/Benchstone.BenchF.Whetsto.Test.html) — `Ubuntu-x64-Viper`; +13.9%; 696,732,421 → 793,903,250; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- [`System.Collections.TryAddDefaultSize.ConcurrentDictionary(Count: 512)`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Collections.TryAddDefaultSize%28String%29.ConcurrentDictionary%28Count%3A%20512%29.html) — `Ubuntu-x64-Viper`; +6.3%; 56,799 → 60,360; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- [`System.Collections.AddGivenSize.ConcurrentDictionary(Size: 512)`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Collections.AddGivenSize%28String%29.ConcurrentDictionary%28Size%3A%20512%29.html) — `Ubuntu-x64-Viper`; +6.0%; 51,929 → 55,058; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- [`System.Collections.TryAddGiventSize.ConcurrentDictionary(Count: 512)`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Collections.TryAddGiventSize%28String%29.ConcurrentDictionary%28Count%3A%20512%29.html) — `Ubuntu-x64-Viper`; +5.9%; 52,211 → 55,295; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- _…and 1 more related regressions in this date group._

- [ ] **Regression group 2026-06-25** — 5 actionable of 7 related regressions; worst +20.0%; queues `Ubuntu-x64-Viper`. **Review notes:** Specific tiem is March 26th, 15:05 on the graph
- Potential existing issues within ±7 days: [dotnet/runtime#129860](https://github.com/dotnet/runtime/issues/129860), [dotnet/perf-autofiling-issues#75373](https://github.com/dotnet/perf-autofiling-issues/issues/75373), [dotnet/perf-autofiling-issues#75558](https://github.com/dotnet/perf-autofiling-issues/issues/75558), [dotnet/perf-autofiling-issues#75877](https://github.com/dotnet/perf-autofiling-issues/issues/75877), [dotnet/perf-autofiling-issues#76014](https://github.com/dotnet/perf-autofiling-issues/issues/76014), [dotnet/perf-autofiling-issues#75366](https://github.com/dotnet/perf-autofiling-issues/issues/75366) _…and 3 more nearby candidates._
- [`System.Memory.Slice.MemoryStartLengthSpan`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Memory.Slice%28Byte%29.MemoryStartLengthSpan.html) — `Ubuntu-x64-Viper`; +20.0%; 5.71 → 6.85; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- [`System.Memory.Slice.ReadOnlyMemoryStartLengthSpan`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Memory.Slice%28Byte%29.ReadOnlyMemoryStartLengthSpan.html) — `Ubuntu-x64-Viper`; +18.0%; 5.69 → 6.72; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- [`System.Memory.Slice.MemoryStartSpan`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Memory.Slice%28Byte%29.MemoryStartSpan.html) — `Ubuntu-x64-Viper`; +11.3%; 5.95 → 6.62; mark **covered**
- [`System.MathBenchmarks.Single.Pow`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.MathBenchmarks.Single.Pow.html) — `Ubuntu-x64-Viper`; +9.0%; 33,065 → 36,033; mark **covered**
- [`System.Collections.AddGivenSize.ConcurrentDictionary(Size: 512)`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Collections.AddGivenSize%28String%29.ConcurrentDictionary%28Size%3A%20512%29.html) — `Ubuntu-x64-Viper`; +6.0%; 51,929 → 55,058; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- [`System.Collections.TryAddGiventSize.ConcurrentDictionary(Count: 512)`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/System.Collections.TryAddGiventSize%28String%29.ConcurrentDictionary%28Count%3A%20512%29.html) — `Ubuntu-x64-Viper`; +5.9%; 52,211 → 55,295; mark **needs-investigation**; note: Specific tiem is March 26th, 15:05 on the graph
- _…and 1 more related regressions in this date group._

- [ ] **Regression group 2025-12-13** — 1 actionable of 1 related regressions; worst +5.1%; queues `Ubuntu-x64-Viper`. **Review notes:** Only current regression time is AFAIK uninvestigated.
- [`PerfLabTests.CastingPerf2.CastingPerf.FooObjIsNull`](https://pvscmdupload.z22.web.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_AOT=true_CompilationMode=wasm_RunKind=micro/ViperUbuntu/PerfLabTests.CastingPerf2.CastingPerf.FooObjIsNull.html) — `Ubuntu-x64-Viper`; +5.1%; 135,678 → 142,639; mark **truly-missed**; note: Only current regression time is AFAIK uninvestigated.

Start with the unchecked items in the Needs investigation and Autofiling issues needing transfer or resolution sections, following each linked issue and representative chart. Review the stated notes and statuses to decide whether each item needs investigation, filing, transfer, acceptance, or closure. Done means the checklist accurately records completed investigation, ownership, filing, and verification work.

Written by the indexing model from the issue text.