SIMT Source Read Scheduling for Operand Arbitration Bottlenecks
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Solution Overview
Problem
Accesses to source operands in single-instruction multiple-thread (SIMT) pipelines cause pipeline bottlenecks due to the need for instructions to wait until all operands are available before proceeding, leading to inefficiencies in instruction throughput and increased power consumption.
Innovation Solution
Implementing granular source read scheduling where instructions send source capture commands as soon as they win arbitration for one operand, even if others are still pending, using per-resource arbitration circuitry and instruction tracker circuitry to manage multiple SIMT slots and buffer operands, allowing instructions to proceed once all are available.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If instructions wait until all operands are available before proceeding, then operand availability is ensured, but instruction throughput decreases
Solution Approach 1:
The patent segments the operand acquisition process by allowing instructions to proceed through pipeline stages while individual source operands are retrieved independently. Each source operand can be captured separately as it becomes available, rather than requiring all operands to be ready before the instruction progresses. This segmentation decouples instruction progression from complete operand availability.
Solution Approach 2:
The patent implements preliminary action by capturing source operands as soon as they become available, even before the instruction is fully ready to execute. The source capture circuitry retrieves operands in advance and holds them in buffer, allowing the instruction to proceed without waiting for all operands to be fully prepared and validated.
2Reliability
If instructions wait for all operands before proceeding, then data correctness is maintained, but power consumption increases
Solution Approach 1:
The patent segments the instruction processing into independent operand capture operations that can proceed asynchronously. Each source operand is captured independently when available, allowing the system to avoid holding the entire instruction in a high-power waiting state. The instruction can progress through lower-power pipeline stages while operands are retrieved separately.
Solution Approach 2:
The patent maintains continuity of useful action by allowing the instruction to continuously progress through pipeline stages rather than stalling. The source capture circuitry continuously retrieves operands as they become available, ensuring that the instruction execution flow remains active and avoids idle high-power states associated with waiting for operand readiness.
3Stability of the object's composition
If instructions are held until all operands are ready, then pipeline bottlenecks are avoided, but pipeline efficiency decreases
Solution Approach 1:
The patent segments operand retrieval from instruction progression, allowing them to occur independently. The source capture circuitry operates separately from the main instruction flow, capturing operands as they become available without requiring the instruction to stall. This segmentation allows pipeline stages to maintain stable operation while improving overall throughput.
Data Source
AI summary
Techniques are disclosed relating to accessing source data in single-instruction multiple-thread (SIMT) pipelines. In some embodiments, multiple categories of operand resource circuits are configured to provide operands for instructions executed by processor pipeline circuitry. Per-resource arbitration circuitry may arbitrate between the SIMT execution slots for access to different operand resources. Source access circuitry may access operand data from operand resources based on source capture commands and source control circuitry may prior to a first SIMT group winning arbitration for all its operands, send a source capture command to the source access circuitry in response to the first SIMT group winning arbitration at the per-resource arbitration circuitry for a first operand resource. Instruction control circuitry may send an instruction release command down the processor pipeline circuitry for the first SIMT group, in response to the first SIMT group winning arbitration for all its operands.