Unlocking Shader Performance with NVIDIA Nsight Graphics

Summary: NVIDIA Nsight Graphics is a powerful tool designed to help developers identify and resolve shader-related performance issues. This article delves into the Shader Profiler feature of Nsight Graphics, explaining how it can be used to pinpoint hotspots in shaders and optimize their performance. We’ll explore the steps to use the Shader Profiler, understand its various components, and discuss how it can significantly improve the debugging process for complex shaders.

Understanding the Shader Profiler

The Shader Profiler in NVIDIA Nsight Graphics is a critical tool for developers aiming to enhance the performance of their shaders. It allows for the examination of the most expensive shaders at each moment in a frame, providing insights into why performance may not meet expectations.

Step 1: Setting Up the GPU Trace Analysis Tool

To begin, it’s essential to start with the GPU Trace Analysis tool. This step helps understand the performance limiters of any given DX12 or VK workload. By setting up a connection to the app to be profiled and choosing the appropriate parameters, developers can launch their game with the necessary HUD for analysis.

Step 2: Switching to the Shader Profiler

Before using the Shader Profiler, ensure that Nsight Graphics can access symbols for your shaders. This can be achieved by compiling shaders with the /Zi option and embedding symbols in the shader binary. Alternatively, symbols can be placed in an external PDB file, with the correct path specified under Tools, Options.

Once symbols are accessible, connect to the application again, choose Frame Profiler under Activity, and launch the Frame Profiler. Navigate to the part of the application to profile, press F11 to capture a frame for analysis, and then select Profile Shaders in Nsight Graphics.

Exploring the Shader Profiler Components

The Shader Profiler presents a summary view after a short sampling session. This view includes:

  • Function Summary: A list of the top shaders, ordered by the number of samples that hit those shaders. This serves as a good proxy for shader latency, helping developers focus on shaders that can yield the biggest benefit from optimizing.
  • Correlation: This column shows green ticks when Nsight Graphics has successfully correlated samples back to the source code. This correlation is crucial for understanding what’s happening in the shader.

Using the Real-Time Shader Profiler

The Real-Time Shader Profiler, available in Nsight Graphics 2023.3 and later, is a temporal sampling profiler for GPU shaders. It enables the examination of the most expensive shaders at each moment in a frame, providing detailed insights into shader performance.

Analyzing Shader Execution

The Shader Profiler also allows for the analysis of shader execution stall reasons directly within the GPU Trace timeline. This feature helps developers quickly understand why shaders may be underperforming and how to improve performance by reducing latency.

Practical Applications

Identifying Hotspots

The Shader Profiler is particularly useful for identifying hotspots in shaders. By examining the most expensive shaders and understanding why they’re hot, developers can direct optimization efforts more effectively.

Debugging Complex Shaders

The Shader Debugger in Nsight Graphics, available in Beta for Vulkan applications, enables real-time debugging of complex shaders. This tool supports ray tracing, raster, and compute shaders, with mesh shader support coming soon. It allows developers to quickly pinpoint and solve issues such as incorrect normal calculations, ambient occlusion errors, and texture mapping issues.

Ray Tracing Efficiency

The Ray Tracing Inspector in Nsight Graphics helps analyze ray tracing efficiency, improve acceleration structures, optimize axis-aligned bounding boxes (AABBs), build flags, and overlaps. This ensures the best image fidelity and frame performance.

Conclusion

The Shader Profiler in NVIDIA Nsight Graphics is a powerful tool for identifying and resolving shader-related performance issues. By understanding how to use the Shader Profiler and leveraging its various components, developers can significantly improve the debugging process for complex shaders. This article has provided a detailed look at the steps to use the Shader Profiler, its practical applications, and how it can enhance shader performance. With the right tools and knowledge, developers can optimize their shaders more effectively, leading to better overall performance and efficiency.