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buzzword [2015/04/16 17:42]
kevincha [Lecture 29 (4/13 Fri.)]
buzzword [2015/04/27 14:20] (current)
rachata
Line 1354: Line 1354:
   * Maximum slowdown and fairness metric   * Maximum slowdown and fairness metric
     ​     ​
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 +
 +===== Lecture 32 (4/20 Mon.) =====
 +
 +  * Heterogeneous systems
 +    * Asymmetric cores: different types of cores on the chip
 +      * Each of these cores are optimized for different workloads/​requirements/​goals
 +      * Multiple special purpose processors
 +      * Flexible and can adapt to workload behavior
 +      * Disadvantages:​ complex and high overhead
 +    * Examples: CPU-GPU systems, heterogeneity in execution models
 +    * Heterogeneous resources
 +      * Example: reliable and non-reliable DRAM in the same system
 +  * Key problems in modern systems
 +    * Memory system
 +    * Efficiency
 +    * Predictability
 +    * Assymmetric design can help solving these problems
 +  * Serialized code sections
 +    * Bottleneck in multicore execution
 +    * Parallelizable vs. serial portion
 +    * Accelerate critical section
 +    * Cache ping-ponging
 +      * Synchronization latency
 +    * Symmetric vs. assymmetric design
 +  * Large cores + small cores
 +    * Core assymmetry
 +  * Amdahl'​s law with heterogeneous cores
 +  * Parallel bottlenecks
 +    * Resource contention
 +      * Depends on what are running
 +  * Accelerated critical section
 +    * Ship critical sections to large cores
 +    * Small modifications and low overhead
 +    * False serialization might become the bottleneck
 +    * Can reduce parallel throughput
 +    * Effect on private cache misses and shared cache misses
 +    ​
 +  ​
 +===== Lecture 33 (4/27 Mon.) =====
 +
 +  * Interconnects
 +    * Connecting multiple components together
 +    * Goal: Scalability,​ flexibility,​ performance and energy efficiency
 +  * Metric: Performance,​ bandwidth, bisection bandwidth, cost, energy efficienct, system performance,​ contention, latency
 +    * Saturation point
 +      * Saturation throughput
 +  * Topology
 +    * How to wire components together, affects routing, throughput, latency
 +    * Bus: All nodes connected to a single ring
 +      * Hard to increase frequency, bandwidth, poor scalability but simple
 +    * Point-to-point
 +      * Low contention and potentially low latency. Costly, not scalable and hard to wire.
 +    * Crossbar
 +      * No contention. Concurrent request from different src/dest can be sent concurrently. Costly.
 +    * Multistage logarithmic network
 +      * Indirect network, low contention, multiple request can be sent concurrently. More scalable compared to crossbar.
 +      * Circuit switch
 +      * Omega network, delta network.
 +      * Butterfly network
 +      * Intermediate switch between sources and destinations
 +    * Switching vs. topology
 +    * Ring
 +      * Each node connected to two other nodes, forming a ring
 +      * Low overhead, high latency, not as scalable.
 +      * Unidirectional ring and bi-directional ring
 +    * Hierarchical Rings
 +      * Layers of rings. More scalable, lower latency.
 +      * Bridge router connect multiple rings together
 +    * Mesh
 +      * 4 input and output ports
 +      * More bisection bandwidth and more scalable
 +      * Easy to layout
 +      * Path diversity
 +      * Routers are more complex
 +    * Tree
 +      * Another hierarchical topology
 +      * Specialized topology
 +      * Good for local traffic
 +      * Fat tree: higher level have more bandwidth
 +      * CM-5 Fat tree
 +        * Fat tree with 4x2 switches
 +    * Hypercube
 +      * N-Dimensional cubes
 +      * Caltech cosmic cube
 +      * Very complex
 +  * Routing algorithm
 +    * How does message get sent from source to destination
 +    * Static or adaptive
 +    * Handling contention
 +      * Buffering helps handling contention, but adds complexity
 +    * Three types of routing algorithms
 +      * Deterministic:​ always takes the same path
 +      * Oblivious: takes different paths without taking into account of the state of the network
 +        * For example, Valiant algorithm
 +      * Adaptive: takes different paths taking into account of the state of the network
 +        * Non-minimal adaptive routing vs. minimal adaptive routing
 +      * Minimal path: path that has minimum number of hops
 +  * Buffering and flow control
 +    * How to store within the network
 +    * Handling oversubscription
 +    * Source throttling
 +    * Bufferless vs. buffered crossbars
 +    * Buffer overflow
 +    * Bufferless deflection routing
 +      * Deflect packets when there is contention
 +      * Hot-potato routing
 +
  
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buzzword.1429220573.txt.gz ยท Last modified: 2015/04/16 17:42 by kevincha