The frame times of my toy ray tracer increased from 24ms to 30ms

[BTOdell]

Description

I was encouraged to open an issue here by people on Reddit: https://www.reddit.com/r/csharp/comments/ypqn03/net_7_is_out_now/ivl99xy/

Here is the link to my repo: https://github.com/BTOdell/SharpRay

With the GA release of .NET 7, I decided to upgrade the version of my toy ray tracing project from .NET 6.0.403 to 7.0.100 in the hopes that I could get some "free" performance with the new version.
Unfortunately, the frame times of my app increased from 24ms to 30ms on my machine when I change the target framework from 6.0 to 7.0.

Configuration

.NET versions: 6.0.403 and 7.0.100
OS: Windows x64 build 19043
CPU: Intel i9-9960X with 64GB DDR4-3600

Regression?

The regression appears to happen when targeting a newer framework: net6.0 to net7.0
If the target framework is set to net6.0, then the performance is the same on both versions of the runtime.

Images

.NET 6.0.403 (target net6.0):

.NET 7.0.100 (target net6.0):

.NET 7.0.100 (target net7.0):

dotnet restore was used before each run to ensure the correct configuration was applied.

Analysis

Sorry if this issue isn't related to the runtime. It might have to do with the C# language compilation to IL?

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[AndyAyersMS]

This is a result of the new On-Stack Replacement feature (aka OSR) in .NET 7. You can disable this feature by adding the following lines to your csproj

  <PropertyGroup>
    <TieredCompilationQuickJitForLoops>false</TieredCompilationQuickJitForLoops>
  </PropertyGroup>

When I do this, I see ~5% faster times for .NET 7.

[edit: fixed the property name and value]

FYI @dotnet/jit-contrib -- I have not yet drilled in to see where OSR is losing perf.

[ghost]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

I was encouraged to open an issue here by people on Reddit: https://www.reddit.com/r/csharp/comments/ypqn03/net_7_is_out_now/ivl99xy/

Here is the link to my repo: https://github.com/BTOdell/SharpRay

With the GA release of .NET 7, I decided to upgrade the version of my toy ray tracing project from .NET 6.0.403 to 7.0.100 in the hopes that I could get some "free" performance with the new version.
Unfortunately, the frame times of my app increased from 24ms to 30ms on my machine when I change the target framework from 6.0 to 7.0.

Configuration

.NET versions: 6.0.403 and 7.0.100
OS: Windows x64 build 19043
CPU: Intel i9-9960X with 64GB DDR4-3600

Regression?

The regression appears to happen when targeting a newer framework: net6.0 to net7.0
If the target framework is set to net6.0, then the performance is the same on both versions of the runtime.

Images

.NET 6.0.403 (target net6.0):

.NET 7.0.100 (target net6.0):

.NET 7.0.100 (target net7.0):

dotnet restore was used before each run to ensure the correct configuration was applied.

Analysis

Sorry if this issue isn't related to the runtime. It might have to do with the C# language compilation to IL?

Author:	BTOdell
Assignees:	-
Labels:	tenet-performance, area-CodeGen-coreclr
Milestone:	-

[AndyAyersMS]

Related: #67594.

[AndyAyersMS]

Profile of 20 seconds of the app on .NET 7 (with default behavior)

I think perfview's attribution of Run as "ReadyToRun" is wrong, this is OSR code.

Corresponding profile from .NET 6

Looking at Run the inner loop codegen is actually fairly similar, except that the OSR method seems to have realized that Vec4.One is a constant -- but then it fails to hoist/CSE this constant and reloads it repeatedly. That might be the regression. It's possible hoisting is thrown off by lack of a preheader or something.

[AndyAyersMS]

This seems to be fixed with latest .NET 8 builds (will be available in Preview 4)

;; 7.0
Framebuffer size: <800, 800>
Rendered in: 138.3371ms
Rendered in: 115.2097ms
Rendered in: 60.8962ms
Rendered in: 27.6196ms
Rendered in: 27.1536ms
Rendered in: 27.0591ms
Rendered in: 27.4292ms
Rendered in: 27.1339ms
Rendered in: 27.1519ms

;; 8.0 current main
Framebuffer size: <800, 800>
Rendered in: 133.7311ms
Rendered in: 108.3345ms
Rendered in: 65.7654ms
Rendered in: 24.2893ms
Rendered in: 26.8595ms
Rendered in: 24.5418ms
Rendered in: 23.7889ms
Rendered in: 24.2502ms
Rendered in: 23.6659ms
Rendered in: 23.9037ms
Rendered in: 23.8969ms

I' m going to close this. @BTOdell once Preview 4 is out give it a try and see if you see the same. If not, please re-open.