ECE506 CSC/ECE 506 Spring 2012/11a az: Difference between revisions
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= Introduction = | = Introduction = | ||
== Distributed shared memory systems == | |||
=== Cache coherence === | |||
DSM systems must maintain cache coherence just as it required by bus-based multiprocessor systems. Cache incoherence is a problem that arises when it is undefined how a change of a value in a specific processor's cache is propagated to the other caches [1, p. 183]. If multiple processors access and modify a shared location in memory and produce outputs based on that shared variable, it is possible to calculate incorrect values if cache coherence is not maintained. | |||
In order to maintain cache coherence, a cache coherence protocol is implemented in hardware (or in specific cases, in software). In DSM systems, the cache coherence controller interfaces with the processor and it's cache, but also has a communication link to the other nodes through an interconnect network. It receives and acts upon requests from the local processor, as well as receives and acts on requests or messages sent across the interconnects with other nodes. | |||
=== Memory consistency === | |||
=== Interconnections === | |||
== Performance Concerns == | == Performance Concerns == | ||
=== Maintaining cache coherence === | === Maintaining cache coherence === | ||
=== Maintaining memory consistency === | === Maintaining memory consistency === | ||
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=== Maintaining memory consistency === | === Maintaining memory consistency === | ||
==== Relaxed memory models with fine granularity coherence ==== | |||
=== Latency of interconnections === | === Latency of interconnections === | ||
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= Definitions = | = Definitions = | ||
; DSM : Distributed shared memory, a parallel computer architecture which consists of a set of nodes that | ; DSM : Distributed shared memory, a parallel computer architecture which consists of a set of nodes that maintain their own local memory, but all nodes are connected together, making their memories one shared addressable space. | ||
; granularity : FIXME | |||
; node: A compute unit that makes up one components of a DSM system. A node consists of one or more sets of processors, cache, and memory. A node is connected to the larger DSM system through an interconnect. | ; node: A compute unit that makes up one components of a DSM system. A node consists of one or more sets of processors, cache, and memory. A node is connected to the larger DSM system through an interconnect. | ||
Revision as of 02:43, 15 April 2012
11a. Performance of DSM systems. Distributed shared memory systems combine the programming models of shared memory systems, and the scalability of distributed systems. However, since DSM systems need extra coordination between software layer and underlying hardware, achieving good performance could be a big challenge. The factors that harm the performance could be the overhead to maintain cache coherence, memory consistency, and the latency of interconnections. Please further explore the factors that can affect the performance of DSM systems, and the improvements that have been made on the existing systems.
Introduction
Cache coherence
DSM systems must maintain cache coherence just as it required by bus-based multiprocessor systems. Cache incoherence is a problem that arises when it is undefined how a change of a value in a specific processor's cache is propagated to the other caches [1, p. 183]. If multiple processors access and modify a shared location in memory and produce outputs based on that shared variable, it is possible to calculate incorrect values if cache coherence is not maintained.
In order to maintain cache coherence, a cache coherence protocol is implemented in hardware (or in specific cases, in software). In DSM systems, the cache coherence controller interfaces with the processor and it's cache, but also has a communication link to the other nodes through an interconnect network. It receives and acts upon requests from the local processor, as well as receives and acts on requests or messages sent across the interconnects with other nodes.
Memory consistency
Interconnections
Performance Concerns
Maintaining cache coherence
Maintaining memory consistency
Latency of interconnections
Performance Improvements
Maintaining cache coherence
Maintaining memory consistency
Relaxed memory models with fine granularity coherence
Latency of interconnections
Definitions
- DSM
- Distributed shared memory, a parallel computer architecture which consists of a set of nodes that maintain their own local memory, but all nodes are connected together, making their memories one shared addressable space.
- granularity
- FIXME
- node
- A compute unit that makes up one components of a DSM system. A node consists of one or more sets of processors, cache, and memory. A node is connected to the larger DSM system through an interconnect.
References
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