Block Organized Source View Data Structure for Processor Dependency Tracking
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Solution Overview
Problem
Current processor architectures face inefficiencies in handling multiple tasks due to the overhead of context switching and the complexity of managing large numbers of threads, particularly in fine-grain parallelism, where hardware thread-aware architectures with duplicate context-state storage do not effectively support non-threaded software code and result in significant software overhead.
Innovation Solution
The method involves grouping instructions into blocks and using a block organized source view data structure to track instruction dependencies through register templates, allowing for efficient dependency broadcasting and reduced overhead in context switching by managing instructions at a higher level of abstraction, thereby simplifying out-of-order execution and reducing management complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If hardware duplicates all architecture state elements for each supported thread, then context switch overhead is eliminated for hardware-supported threads, but area, power, and complexity increase significantly
Solution Approach 1:
The architecture state is segmented into multiple levels: fully duplicated state for hardware-supported threads, partially duplicated state for software threads, and shared state for common operations. This segmentation allows the system to eliminate context switch overhead for hardware threads while avoiding full duplication for software threads, thus reducing area, power, and complexity.
Solution Approach 2:
The patent introduces a new dimension of thread management by implementing a hierarchical thread state structure with multiple levels of duplication. Instead of a binary choice between full duplication and no duplication, the system creates intermediate levels of state sharing, adding a dimensional layer to thread state management that resolves the contradiction between eliminating context switches and reducing hardware complexity.
2Loss of time
If hardware supports multiple context states for limited threads, then context switching is eliminated, but the number of supported threads is limited and area increases
Solution Approach 1:
The system dynamically allocates hardware thread state resources based on runtime needs. Software threads can be promoted to hardware-supported status when needed, gaining full state duplication and zero context switch overhead, while less critical threads remain in the software thread pool with partial state sharing. This dynamic allocation allows the system to support a large number of threads while eliminating context switches for the most critical ones.
3Productivity
If software threads exceed hardware-supported threads, then context switch must still be performed, but fine grain parallelism requires large number of threads
Solution Approach 1:
The patent implements partial context switching by maintaining hardware thread state for only the most critical threads while using software thread state for less critical ones. This partial action approach allows the system to support fine-grain parallelism with many software threads while eliminating context switches for hardware-supported threads, achieving high productivity without excessive context switching overhead.
4Loss of time
If hardware duplicates architecture state for each thread, then context switch is eliminated, but power consumption increases
Solution Approach 1:
The system applies local quality by providing full state duplication only where it is most needed - for hardware-supported threads that require zero context switch overhead. Software threads receive partial state sharing, duplicating only the critical state elements needed for their operation. This localized approach to state duplication eliminates context switches for critical threads while minimizing power consumption for less critical threads.
Data Source
AI summary
A method for dependency broadcasting through a block organized source view data structure. The method includes receiving an incoming instruction sequence using a global front end; grouping the instructions to form instruction blocks; using a plurality of register templates to track instruction destinations and instruction sources by populating the register template with block numbers corresponding to the instruction blocks, wherein the block numbers corresponding to the instruction blocks indicate interdependencies among the blocks of instructions; populating a block organized source view data structure, wherein the source view data structure stores sources corresponding to the instruction blocks as recorded by the plurality of register templates; upon dispatch of one block of the instruction blocks, broadcasting a number belonging to the one block to a column of the source view data structure that relates that block and marking the column accordingly; and updating the dependency information of remaining instruction blocks in accordance with the broadcast.