Department of Electrical and Computer Engineering Computer Architecture and Parallel Systems Laboratory - CAPSL Guang R. Gao ACM Fellow and IEEE Fellow Endowed Distinguished Professor Electrical & Computer Engineering University of Delaware [email protected]Topic A – Part 3 Dataflow Model of Computation (From Dataflow to Multithreading) Topic-Gao-Dataflow-part3 1 3/21/2014 CPEG 852 - Spring 2014 Advanced Topics in Computing Systems
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Department of Electrical and Computer Engineering Computer Architecture and Parallel Systems Laboratory - CAPSL
Advantages of the McGill Dataflow Architecture Model
• Eliminate unnecessary token copying and transmission overhead.
• Instruction scheduling is separated from the main datapath of the processor (e.g. asynchronous, decoupled).
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Von Neumann Threads as Macro Dataflow Nodes
1
2
3
k
A sequence of
instructions is “packed”
into a macro-dataflow
node
Synchronization is done
at the macro-node level
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The Von Neumann-type Processing
begin for i = 1 … … endfor end
Source Code
Compiler Sequential
Machine
Representation
CPU
Load
Processor
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Hybrid Evaluation Von Neumann Style Instruction Execution” on
the McGill Dataflow Architecture • Group a “sequence” of dataflow instruction into a “thread” or
a macro dataflow node. • Data-driven synchronization among threads. • “Von Neumann style sequencing” within a thread. Advantage: Preserves the parallelism among threads but avoids
unnecessary fine-grain synchronization between instructions within a sequential thread.
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What Do We Get?
• A hybrid architecture model without sacrificing the advantage of fine-grain parallelism!
(latency-hiding, pipelining support)
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A Realization of the Hybrid Evaluation
Pipelined Instruction
Processing Unit (PIPU)
Dataflow Instruction
Scheduling Unit (DISU)
Fire Done
Shortcut
1 2 k
Von Neumann bit
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Case Studies – Dataflow Model Inspired Multithreading
• McGill Dataflow Model (1988 - 1993)
• EARTH Model (1993 – mid 2000s )
• The UHPC/Runnemede Model (2010 - )
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CPU
Memory
Fine-Grain non-preemptive thread-
The “hotel” model
Thread
Unit
Executor
Locus
Coarse-Grain vs. Fine-Grain Multithreading
A Pool
Thread
CPU
Memory
Executor
Locus
A Single
Thread
Coarse-Grain thread-
The family home model
Thread
Unit
[Gao: invited talk at Fran Allen’s Retirement Workshop, 07/2002]