Graphics Processor TLB Clear Code Memory Access Compression
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Solution Overview
Problem
Current graphics processing systems face inefficiencies in memory access due to the need for frequent access to off-die memory during rendering operations, particularly in tile-based rendering techniques, which increases memory bandwidth requirements.
Innovation Solution
Implementing memory access compression using clear codes for pixel tiles, where a graphics processor tracks cached shader data to determine if a surface is cleared, allowing it to bypass memory accesses for clear pages by checking the Translation Lookaside Buffer (TLB) entry, and storing clear color data in page table entries or registers to quickly retrieve clear values during address translation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tile-based rendering techniques are used to process graphics data, then processing efficiency is improved, but memory bandwidth requirements increase due to frequent off-die memory accesses
Solution Approach 1:
The patent applies preliminary action by pre-clearing pixel tiles to a default background color before rendering operations. This allows the rendering system to skip writing to memory regions that will remain unchanged, thereby reducing memory bandwidth usage while maintaining processing efficiency. The clear code mechanism pre-establishes the background state, eliminating the need for subsequent memory writes to clear pages.
Solution Approach 2:
The patent extracts the clear color information from the rendering pipeline and stores it in the Translation Lookaside Buffer (TLB) alongside address translation data. By separating and caching the clear color data in the TLB, the system can quickly determine whether a page is clear without accessing full surface data in memory, thereby reducing memory bandwidth requirements while maintaining rendering efficiency.
2Ease of operation
If clear color data is stored in surface data in memory, then clear operations can be performed, but unnecessary memory reads occur for clear pages
Solution Approach 1:
The patent introduces the Translation Lookaside Buffer (TLB) as an intermediary structure that stores both address translation data and clear color information. This intermediary allows the rendering system to quickly check whether a page is clear by examining the TLB entry during address translation, without needing to read the full surface data from memory. This eliminates unnecessary memory reads for clear pages while preserving clear operation capability.
Solution Approach 2:
The patent merges the clear color data with the address translation data in the TLB entry. By combining these two pieces of information into a single cache structure, the system can perform both address translation and clear page detection in a single TLB lookup operation, eliminating the need for separate memory reads and reducing overall memory access time.
3Measurement precision
If full surface data is read from memory to determine clear status, then accurate clear detection is achieved, but memory bandwidth is wasted
Solution Approach 1:
The patent applies preliminary action by pre-processing and storing clear color information in the TLB during address translation setup. This preliminary caching of clear status data allows the rendering system to accurately detect clear pages through a simple TLB lookup without needing to read the full surface data from memory, thereby maintaining detection accuracy while eliminating memory bandwidth waste.
Solution Approach 2:
The patent creates a copy of the clear color information and stores it in the TLB alongside address translation data. This copy mechanism allows the system to accurately determine clear status by reading the copied data from the TLB cache rather than reading the original surface data from memory, maintaining measurement precision while dramatically reducing memory bandwidth consumption.
Data Source
AI summary
One embodiment provides an apparatus comprising a memory device configured to store a page table that includes a set of page table entries and a graphics processing cluster array including a plurality of graphics multiprocessors, the plurality of graphics multiprocessors coupled via a data interconnect. The graphics multiprocessor of the plurality of graphics multiprocessors includes a translation lookaside buffer (TLB) coupled with the memory device, the TLB to cache a first page table entry of the set of page table entries, the first page table entry to indicate that a first virtual page is a valid page that is cleared to a clear color and circuitry to bypass an access to the memory device for the first virtual page and determine a color associated with the first virtual page based on the indication that the first virtual page is a valid page that is cleared to the clear color.