Add configurable EventPipe CPU sampling rate via `DOTNET_EventPipeThreadSamplingRate` by pavelsavara · Pull Request #127292 · dotnet/runtime

pavelsavara · 2026-04-22T17:55:40Z

Summary

This change introduces a new DOTNET_EventPipeThreadSamplingRate environment variable that allows overriding the default EventPipe CPU sample profiler interval.

The default 1ms is too quick for WASM/browser.

This split from #126324 for smaller code review.

Changes

New config: `DOTNET_EventPipeThreadSamplingRate`

src/coreclr/inc/clrconfigvalues.h — Register the new INTERNAL_EventPipeThreadSamplingRate DWORD config (default 0).
src/native/eventpipe/ep-rt.h — Declare ep_rt_config_value_get_sampling_rate() in the shared EventPipe runtime abstraction header.
src/native/eventpipe/ep.c — In ep_init(), read the configured rate and convert from milliseconds to nanoseconds. Falls back to the per-platform default when the value is 0.

Per-runtime implementations of `ep_rt_config_value_get_sampling_rate`

src/coreclr/vm/eventing/eventpipe/ep-rt-coreclr.h — CoreCLR: reads via CLRConfig::GetConfigValue.
src/coreclr/nativeaot/Runtime/eventpipe/ep-rt-aot.h — NativeAOT: reads via RhConfig::Environment::TryGetIntegerValue.
src/mono/mono/eventpipe/ep-rt-mono.h — Mono: reads via g_getenv("DOTNET_EventPipeThreadSamplingRate").

Blazor/Browser WASM build integration

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets
- Gate _AddWasmDiagnosticPortsEnvironmentVariable target on EnableDiagnostics=true.
- Parse WasmPerformanceInstrumentation to extract an optional ,interval=<ms> suffix.
- Pass the filter portion as DOTNET_WasmPerformanceInstrumentation and the interval (if present) as DOTNET_EventPipeThreadSamplingRate.

Miscellaneous fixes

src/native/eventpipe/ds-ipc-pal-websocket.h
- Wrap websocket extern declarations in extern "C" to prevent C++ name mangling (needed for JS interop in browser WASM).
- Fix ds_rt_websocket_recv signature: remove incorrect const from the receive buffer parameter.
src/coreclr/vm/eventing/eventpipe/ep-rt-coreclr.h
- Add PROFILING_SUPPORTED preprocessor guard around ep_rt_notify_profiler_provider_created body.
- Update #endif comments for clarity.
src/native/eventpipe/ep-session.c
- Add EP_ASSERT(session->buffer_manager != NULL) invariant check in the streaming loop shutdown path.

dotnet-policy-service · 2026-04-22T17:56:43Z

Tagging subscribers to this area: @steveisok, @dotnet/area-system-diagnostics
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Adds a new runtime-configurable knob (DOTNET_EventPipeCpuSamplingRate) to override EventPipe CPU sample-profiler interval (intended to allow slower sampling on WASM/browser), and wires it through CoreCLR/NativeAOT/Mono plus browser WASM build plumbing.

Changes:

Introduce EventPipeCpuSamplingRate config/env var and consume it in EventPipe init (ms → ns conversion, 0 = default).
Implement ep_rt_config_value_get_sampling_rate() for CoreCLR, NativeAOT, and Mono runtime layers.
Update browser WASM SDK targets to pass DOTNET_EventPipeCpuSamplingRate (and related instrumentation env vars) and adjust websocket interop declarations.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/native/eventpipe/ep.c	Reads configurable sampling interval and applies it during `ep_init()`.
src/native/eventpipe/ep-session.c	Adds an assert in the no-threads streaming loop shutdown path.
src/native/eventpipe/ep-rt.h	Adds runtime abstraction API for sampling-rate config retrieval.
src/native/eventpipe/ds-ipc-pal-websocket.h	Adjusts websocket externs for C++/interop and fixes recv buffer constness.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Adds EnableDiagnostics gating and parses `WasmPerformanceInstrumentation` for optional interval.
src/mono/mono/eventpipe/ep-rt-mono.h	Mono implementation of sampling-rate config getter via env var.
src/coreclr/vm/eventing/eventpipe/ep-rt-coreclr.h	CoreCLR implementation of sampling-rate config getter; minor preprocessor cleanup.
src/coreclr/nativeaot/Runtime/eventpipe/ep-rt-aot.h	NativeAOT implementation of sampling-rate config getter.
src/coreclr/inc/clrconfigvalues.h	Registers new CoreCLR config knob `INTERNAL_EventPipeCpuSamplingRate`.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

…oft.NET.Sdk.WebAssembly.Browser.targets Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Copilot

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

lateralusX

LGTM!

jkotas · 2026-04-24T13:42:29Z

Document this in https://learn.microsoft.com/en-us/dotnet/core/diagnostics/eventpipe#trace-using-environment-variables ?

noahfalk

Looks good to me modulo comments inline.

# Conflicts: # src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 6 comments.

pavelsavara · 2026-04-27T18:02:53Z

Document this in https://learn.microsoft.com/en-us/dotnet/core/diagnostics/eventpipe#trace-using-environment-variables ?

dotnet/docs#53393

DOTNET_EventPipeCpuSamplingRate

6363c47

pavelsavara added this to the 11.0.0 milestone Apr 22, 2026

pavelsavara self-assigned this Apr 22, 2026

Copilot AI review requested due to automatic review settings April 22, 2026 17:55

pavelsavara added the area-System.Diagnostics label Apr 22, 2026

Copilot started reviewing on behalf of pavelsavara April 22, 2026 17:56 View session

Copilot AI reviewed Apr 22, 2026

View reviewed changes

Comment thread src/native/eventpipe/ep-session.c Outdated

Comment thread ...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets Outdated

Comment thread src/mono/mono/eventpipe/ep-rt-mono.h

Update src/native/eventpipe/ep-session.c

6c03fdc

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings April 22, 2026 18:31

Update src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Micros…

9a89ca5

…oft.NET.Sdk.WebAssembly.Browser.targets Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot started reviewing on behalf of pavelsavara April 22, 2026 18:32 View session

Copilot AI reviewed Apr 22, 2026

View reviewed changes

Comment thread ...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

Comment thread src/mono/mono/eventpipe/ep-rt-mono.h Outdated

fix

53cf068

Merge branch 'main' into browser_EP_sample_rate

d52ae42

Copilot AI review requested due to automatic review settings April 23, 2026 21:59

Copilot AI reviewed Apr 23, 2026

View reviewed changes

build-analysis Bot mentioned this pull request Apr 24, 2026

Sometimes the helix SDK uses GetWorkItemsAsync when workitems aren't done processing. dotnet/dnceng#6011

Open

3 tasks

pavelsavara marked this pull request as ready for review April 24, 2026 06:28

pavelsavara requested review from akoeplinger, lateralusX, lewing, mdh1418, noahfalk and steveisok as code owners April 24, 2026 06:28

pavelsavara requested a review from MichalStrehovsky as a code owner April 24, 2026 06:28

lateralusX reviewed Apr 24, 2026

View reviewed changes

Comment thread src/native/eventpipe/ep.c

lateralusX reviewed Apr 24, 2026

View reviewed changes

Comment thread src/native/eventpipe/ep-session.c Outdated

maraf reviewed Apr 24, 2026

View reviewed changes

Comment thread ...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets Outdated

pavelsavara added 2 commits April 24, 2026 11:06

Merge branch 'main' into browser_EP_sample_rate

f7dc73c

feedback

77d3a99

Copilot AI review requested due to automatic review settings April 24, 2026 09:19

Copilot started reviewing on behalf of pavelsavara April 24, 2026 09:20 View session

Copilot AI reviewed Apr 24, 2026

View reviewed changes

Comment thread src/native/eventpipe/ep.c Outdated

Comment thread ...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets Outdated

lateralusX reviewed Apr 24, 2026

View reviewed changes

Comment thread src/native/eventpipe/ep.c Outdated

feedback

7297326

This was referenced Apr 24, 2026

[browser] Wasm.Build.Tests timeout - Timed out after 10s waiting for 'WASM EXIT' #116697

Open

Android arm32 device not found (armeabi-v7a architecture unavailable) #125440

Open

lateralusX approved these changes Apr 24, 2026

View reviewed changes

noahfalk approved these changes Apr 27, 2026

View reviewed changes

Comment thread src/coreclr/inc/clrconfigvalues.h Outdated

Comment thread src/coreclr/inc/clrconfigvalues.h Outdated

Comment thread src/coreclr/inc/clrconfigvalues.h Outdated

pavelsavara added 3 commits April 27, 2026 15:11

feedback

6e9b780

Merge branch 'main' into browser_EP_sample_rate

96ab3a8

# Conflicts: # src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

feedback

ffb89e5

Copilot AI review requested due to automatic review settings April 27, 2026 17:44

Copilot started reviewing on behalf of pavelsavara April 27, 2026 17:44 View session

Copilot AI reviewed Apr 27, 2026

View reviewed changes

pavelsavara changed the title ~~Add configurable EventPipe CPU sampling rate via DOTNET_EventPipeCpuSamplingRate~~ Add configurable EventPipe CPU sampling rate via DOTNET_EventPipeThreadSamplingRate Apr 27, 2026

pavelsavara mentioned this pull request Apr 27, 2026

document DOTNET_EventPipeThreadSamplingRate dotnet/docs#53393

Open

This was referenced Apr 27, 2026

slow macOS - "##[error]The job running on agent Azure Pipelines 9 ran longer than the maximum time of 60 minutes." dotnet/dnceng#1883

Open

wasm build failure in CI #117017

Open

fix

25cc16d

pavelsavara merged commit 4e8ab2d into dotnet:main Apr 29, 2026
158 of 160 checks passed

pavelsavara deleted the browser_EP_sample_rate branch April 29, 2026 07:15

Conversation

pavelsavara commented Apr 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Changes

New config: DOTNET_EventPipeThreadSamplingRate

Per-runtime implementations of ep_rt_config_value_get_sampling_rate

Blazor/Browser WASM build integration

Miscellaneous fixes

Uh oh!

dotnet-policy-service Bot commented Apr 22, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

Uh oh!

lateralusX left a comment

Choose a reason for hiding this comment

Uh oh!

jkotas commented Apr 24, 2026

Uh oh!

noahfalk left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

pavelsavara commented Apr 27, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants

pavelsavara commented Apr 22, 2026 •

edited

Loading

New config: `DOTNET_EventPipeThreadSamplingRate`

Per-runtime implementations of `ep_rt_config_value_get_sampling_rate`