buzzword
Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision Next revision Both sides next revision | ||
|
buzzword [2015/04/01 18:17] rachata |
buzzword [2015/04/10 16:37] kevincha |
||
|---|---|---|---|
| Line 1121: | Line 1121: | ||
| * How much did the prefetcher cause misses in the demand misses? | * How much did the prefetcher cause misses in the demand misses? | ||
| * Hard to quantify | * Hard to quantify | ||
| + | |||
| + | |||
| + | ===== Lecture 26 (4/3 Fri.) ===== | ||
| + | |||
| + | * Feedback directed prefetcher | ||
| + | * Use the result of the prefetcher as a feedback to the prefetcher | ||
| + | * with accuracy, timeliness, polluting information | ||
| + | * Markov prefetcher | ||
| + | * Prefetch based on the previous history | ||
| + | * Use markov model to predict | ||
| + | * Pros: Can cover arbitary pattern (easy for link list traversal or trees) | ||
| + | * Downside: High cost, cannot help with compulsory misses (no history) | ||
| + | * Content directed prefetching | ||
| + | * Indentify the content in memory for pointers (which is used as the address to prefetch | ||
| + | * Not very efficient (hard to figure out which block is the pointer) | ||
| + | * Software can give hints | ||
| + | * Correlation table | ||
| + | * Address correlation | ||
| + | * Execution based prefetcher | ||
| + | * Helper thread/speculative thread | ||
| + | * Use another thread to pre-execute a program | ||
| + | * Can be a software based or hardware based | ||
| + | * Discover misses before the main program (to prefetch data in a timely manner) | ||
| + | * How do you construct the helper thread | ||
| + | * Preexecute instruction (one example of how to initialize a speculative thread), slide 9 | ||
| + | * Thread-based pre-execution | ||
| + | * Error tolerance | ||
| + | * Solution to errors | ||
| + | * Tolerate errors | ||
| + | * New interface, new design | ||
| + | * Eliminate or minimize errors | ||
| + | * New technology, system-wide rethinking | ||
| + | * Embrace errors | ||
| + | * Map data that can tolerate errors to error-prone area | ||
| + | * Hybrid memory systesm | ||
| + | * Combining multiple memory technology together | ||
| + | * What can emerging technology help? | ||
| + | * Scalability | ||
| + | * Lower the cost | ||
| + | * Energy efficiency | ||
| + | * Possible solutions to the scaling problem | ||
| + | * Less leakage DRAM | ||
| + | * Heterogeneous DRAM (TL-DRAM, etc.) | ||
| + | * Add more functionality to DRAM | ||
| + | * Denser design (3D stack) | ||
| + | * Different technology | ||
| + | * NVM | ||
| + | * Charge vs. resistice memory | ||
| + | * How data is written? | ||
| + | * How to read the data? | ||
| + | * Non volatile memory | ||
| + | * Resistive memory | ||
| + | * PCM | ||
| + | * Inject current to change the phase | ||
| + | * Scales better than DRAM | ||
| + | * Multiple bits per cell | ||
| + | * Wider resistence range | ||
| + | * No refresh is needed | ||
| + | * Downside: Latency and write endurance | ||
| + | * STT-MRAM | ||
| + | * Inject current to change the polarity | ||
| + | * Memristor | ||
| + | * Inject current to change the structure | ||
| + | * Pros and cons between different technologies | ||
| + | * Persistency - data stay there even without power | ||
| + | * Unified memory and storage management (persistent data structure) - Single level store | ||
| + | * Improve energy and performance | ||
| + | * Simplify programming model | ||
| + | * Different design options for DRAM + NVM | ||
| + | * DRAM as a cache | ||
| + | * Place some data in DRAM and other in PCM | ||
| + | * Based on the characteristics | ||
| + | * Frequently accessed data that need lower write latency in DRAM | ||
| + | | ||
| + | |||
| + | ===== Lecture 27 (4/6 Mon.) ===== | ||
| + | * Flynn's taxonomy | ||
| + | * Parallelism | ||
| + | * Reduces power consumption (P ~ CV^2F) | ||
| + | * Better cost efficiency and easier to scale | ||
| + | * Improves dependability (in case the other core is faulty | ||
| + | * Different types of parallelism | ||
| + | * Instruction level parallelism | ||
| + | * Data level parallelism | ||
| + | * Task level parallelism | ||
| + | * Task level parallelism | ||
| + | * Partition a single, potentially big, task into multiple parallel sub-task | ||
| + | * Can be done explicitly (parallel programming by the programmer) | ||
| + | * Or implicitly (hardware partitions a single thread speculatively) | ||
| + | * Or, run multiple independent tasks (still improves throughput, but the speedup of any single tasks is not better, also simpler to implement) | ||
| + | * Loosely coupled multiprocessor | ||
| + | * No shared global address space | ||
| + | * Message passing to communicate between different sources | ||
| + | * Simple to manage memory | ||
| + | * Tightly coupled multiprocessor | ||
| + | * Shared global address space | ||
| + | * Need to ensure consistency of data | ||
| + | * Programming issues | ||
| + | * Hardware-based multithreading | ||
| + | * Coarse grained | ||
| + | * Find grained | ||
| + | * Simultaneous: Dispatch instruction from multiple threads at the same time | ||
| + | * Parallel speedup | ||
| + | * Superlinear speedup | ||
| + | * Utilization, Redundancy, Efficiency | ||
| + | * Amdahl's law | ||
| + | * Maximum speedup | ||
| + | * Parallel portion is not perfect | ||
| + | * Serial bottleneck | ||
| + | * Synchronization cost | ||
| + | * Load balance | ||
| + | * Some threads has more work, requires more time to hit the sync. point | ||
| + | * Critical sections | ||
| + | * Enforce mutually exclusive access to shared data | ||
| + | * Issues in parallel programming | ||
| + | * Correctness | ||
| + | * Synchronization | ||
| + | * Consistency | ||
| + | |||
| + | |||
| + | ===== Lecture 28 (4/8 Wed.) ===== | ||
| + | |||
buzzword.txt · Last modified: 2015/04/27 18:20 by rachata
Page Tools
Except where otherwise noted, content on this wiki is licensed under the following license: CC Attribution-Share Alike 3.0 Unported
