By default, the Visualization pane shows the bar chart in a time-based view. To see the most expensive events in the frame, it is recommended to set the X-Y axis to GPU Duration by GPU Duration. This allows the tallest and widest bars to represent the events that take up the most time on the GPU.
Hotspot mode groups the events within a frame by bottleneck and/or state, where states are shader sets in DirectX* 11, pipeline state objects (PSO) in DirectX 12, and pipelines in Vulkan. By enabling Hotspot mode, you can identify exactly which bottleneck or state is affecting the GPU most. Each grouping expands to reveal which events contribute to that specific bottleneck/state. With this mode, the events are no longer in time-based order or grouping.
When Hotspot mode is enabled, the metric values are an average/weighted value for the selected region. To determine the affecting bottleneck in each grouping, view the 3D pipeline located in the bottom right-hand side of the Graphics Frame Analyzer Profiling View window. Any portions of the pipeline that are marked in red are considered the main bottleneck and any yellow portions indicate a secondary bottleneck. The amount of green, yellow, and red that make up any pipeline item directly correlates to the number of events that are experiencing that bottleneck i.e. if grouping by stated and only 50% of events in a grouping have a main bottleneck at Thread Dispatch, then only half of the Thread Dispatch bar will be red. Any pipeline state can experience a primary, secondary, or no bottleneck in the same grouping, meaning the state can be marked with red, yellow, and green in varying amounts. Selecting the bottleneck in the 3D pipeline offers helpful suggestions on how to fix the problem.
To enable Hotspot mode, select the hotspot button in the top-left corner of the Profiling View. Once pressed, the bar chart will reorder itself to group by bottleneck and/or state. An alert will show up in the message pane at the top of the Profiling View:
The categorization used to determine hotspots can be changed by selecting the Group By drop-down menu and selecting any of the attributes:
- Bottleneck, State - groups events together that share the same state and bottleneck
- Bottleneck - groups events together that share the same bottleneck, where shared states are used as sub-categories
- State - groups events together that share the same states, where the bottleneck is used as a sub-category
Each grouping can also be expanded to reveal all of the events contributing to the hotspot.
For the Hotspot mode backend flowchart and detailed bottleneck descriptions, see the Intel® Graphics Performance Analyzers Cookbook.