GPU Rasterizer Interrupt Handling via State Save

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Solution Overview

Problem

Current graphics processing units (GPUs) face inefficiencies in handling interrupts during the rasterization process, particularly in coarse rasterization, which can lead to unacceptably long delays in switching contexts and servicing interrupts, especially when processing large primitives on high-resolution displays.

Innovation Solution

The implementation of a method that includes context save and context replay techniques, where the state of the rasterizer is saved during coarse rasterization and restored after servicing interrupts, allowing for quicker interrupt response by saving the state of the rasterizer in a backing store and rerunning the rasterization process from the last completed tile.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the rasterizer completes the current primitive before servicing an interrupt, then the rasterization process maintains simplicity and continuity, but the interrupt response time becomes unacceptably long

Engineering Contradiction:

Improveinterrupt response timeVSAvoidrasterizer complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by saving the rasterizer state at periodic intervals during coarse rasterization, before an interrupt actually occurs. This allows the system to quickly restore to a known good state when an interrupt arrives, rather than having to complete the entire current primitive first. The state saving mechanism is prepared in advance, enabling fast forward recovery.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the rasterization process into manageable units by introducing periodic state save points during coarse rasterization. Instead of treating the entire primitive processing as an atomic operation, it divides the work into segments separated by state checkpoints, allowing interrupt handling to occur at these segmentation points without requiring completion of the full primitive.

Inventive Principle:

Principle #1Segmentation

2Loss of time

If the rasterizer frequently checks for interrupts during coarse rasterization, then interrupt responsiveness is improved, but processing overhead increases

Engineering Contradiction:

Improveinterrupt latencyVSAvoidprocessing overhead

Core Design Contradiction:

Loss of timeVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic action by checking for interrupts at regular, predetermined intervals during coarse rasterization rather than continuously or at every operation. This periodic checking mechanism balances interrupt responsiveness with processing efficiency, ensuring that interrupts are detected within acceptable timeframes while avoiding excessive overhead from overly frequent checks.

Inventive Principle:

Principle #19Periodic action

3Productivity

If the GPU switches contexts quickly to service interrupts, then system responsiveness is improved, but the complexity of state management increases

Engineering Contradiction:

Improvecontext switching speedVSAvoidstate management complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies copying by creating a saved copy of the rasterizer state at periodic intervals during coarse rasterization. When an interrupt requires context switching, the system restores this copied state rather than attempting to save and restore the entire complex state structure. This copying approach simplifies state management while enabling fast context switching.

Inventive Principle:

Principle #26Copying

4Manufacturing precision

If the rasterizer processes large primitives on high-resolution displays, then image quality is improved, but interrupt handling delay increases

Engineering Contradiction:

Improverasterization precisionVSAvoidprimitive processing time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-saving the rasterizer state at periodic intervals during the processing of large primitives. This allows the system to interrupt and service interrupts quickly by restoring to a previously saved state, rather than having to complete the entire large primitive processing sequence. The high-resolution rendering quality is maintained while interrupt responsiveness is improved.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8780123B2Interrupt handling techniques in the rasterizer of a GPU

Publication Date: 2014.07.15 NVIDIA CORP

AI summary

Techniques for handling an interrupt in the rasterizer, in accordance with embodiment of the present technology, start with rasterizing one or more primitives of a first context. If an interrupt is received, state information of the rasterizer is saved in a backing store after coarse rasterizing a given tile. After storing the raster state information, the one or more primitives of a second context are rasterized. After the second context is served, the raster state information of the first context is restored and rasterization of the one or more primitives of the first context is restarted.