buzzword
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buzzword [2015/03/27 18:24] rachata |
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| * Determine which command (across banks) should be sent to DRAM | * Determine which command (across banks) should be sent to DRAM | ||
| + | ===== Lecture 22 (03/25 Wed.) ===== | ||
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| + | * Flash controller | ||
| + | * Flash memory | ||
| + | * Garbage collection in flash | ||
| + | * Overhead in flash memory | ||
| + | * Erase (off the critical path, but takes a long time) | ||
| + | * Different types of DRAM | ||
| + | * DRAM design choices | ||
| + | * Cost/density/latency/BW/Yield | ||
| + | * Sense Amplifier | ||
| + | * How do they work | ||
| + | * Dual data rate | ||
| + | * Subarray | ||
| + | * Rowclone | ||
| + | * Moving bulk of data from one row to others | ||
| + | * Lower latency and BW when performing copies/zeroes out the data | ||
| + | * TL-DRAM | ||
| + | * Far segment | ||
| + | * Near segment | ||
| + | * What causes the long latency | ||
| + | * Benefit of TL-DRAM | ||
| + | * TL-DRAM vs. DRAM cache (adding a small cache in DRAM) | ||
| + | * List of commands to read/write data into DRAM | ||
| + | * Activate -> read/write -> precharge | ||
| + | * Activate moves data into the row buffer | ||
| + | * Precharge prepare the bank for the next access | ||
| + | * Row buffer hit | ||
| + | * Row buffer conflict | ||
| + | * Scheduling memory requests to lower row conflicts | ||
| + | * Burst mode of DRAM | ||
| + | * Prefetch 32-bits from an 8-bit interface if DRAM needs to read 32 bits | ||
| + | * Address mapping | ||
| + | * Row interleaved | ||
| + | * Cache block interleaved | ||
| + | * Memory controller | ||
| + | * Sending DRAM commands | ||
| + | * Periodically send commands to refresh DRAM cells | ||
| + | * Ensure correctness and data integrity | ||
| + | * Where to place the memory controller | ||
| + | * On CPU chip vs. at the main memory | ||
| + | * Higher BW on-chip | ||
| + | * Determine the order of requests that will be serviced in DRAM | ||
| + | * Request queues that hold requests | ||
| + | * Send requests whenever the request can be sent to the bank | ||
| + | * Determine which command (across banks) should be sent to DRAM | ||
| + | * Priority of demand vs. prefetch requests | ||
| + | * Memory scheduling policies | ||
| + | * FCFS | ||
| + | * FR-FCFS | ||
| + | * Try to maximize row buffer hit rate | ||
| + | * Capped FR-FCFS: FR-FCFS with a timeout | ||
| + | * Usually this is done in a command level (read/write commands and precharge/activate commands) | ||
| + | * PAR-BS | ||
| + | * Key benefits | ||
| + | * stall time | ||
| + | * shortest job first | ||
| + | * STFM | ||
| + | * ATLAS | ||
| + | * TCM | ||
| + | * Key benefits | ||
| + | * Configurability | ||
| + | * Fairness + performance at the same time | ||
| + | * Robuestness isuees | ||
| + | * Open row policy | ||
| + | * Closed row policy | ||
| + | * QoS | ||
| + | * QoS issues in memory scheduling | ||
| + | * Fairness | ||
| + | * Performance guarantee | ||
| + | |||
| + | |||
| + | ===== Lecture 23 (03/27 Fri.) ===== | ||
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| + | * Different ways to control interference in DRAM | ||
| + | * Partitioning of resource | ||
| + | * Channel partitioning: map applications that interfere with each other in a different channel | ||
| + | * Keep track of application's characteristics | ||
| + | * Dedicate a channel might waste the bandwidth | ||
| + | * Need OS support to determine the channel bits | ||
| + | * Source throttling | ||
| + | * A controller throttle the core depends on the performance target | ||
| + | * Example: Fairness via source throttling | ||
| + | * Detect unfairness and throttle application that is interfering | ||
| + | * How do you estimate slowdown? | ||
| + | * Threshold based solution: hard to configure | ||
| + | * App/thread scheduling | ||
| + | * Critical threads usually stall the progress | ||
| + | * Designing DRAM controller | ||
| + | * Has to handle the normal DRAM operations | ||
| + | * Read/write/refresh/all the timing constraints | ||
| + | * Keep track of resources | ||
| + | * Assign priorities to different requests | ||
| + | * Manage requests to banks | ||
| + | * Self-optimizing controller | ||
| + | * Use machine learning to improve DRAM controller | ||
| + | * A-DRM | ||
| + | * Architecture aware DRAM | ||
| + | * Multithread | ||
| + | * synchronization | ||
| + | * Pipeline programs | ||
| + | * Producer consumer model | ||
| + | * Critical path | ||
| + | * Limiter threads | ||
| + | * Prioritization between threads | ||
| + | * Different power mode in DRAM | ||
| + | * DRAM Refresh | ||
| + | * Why does DRAM has to refresh every 64ms | ||
| + | * Banks are unavailable during refresh | ||
| + | * LPDDR mitigate this by using a per-bank refresh | ||
| + | * Has to spend longer time with bigger DRAM | ||
| + | * Distributed refresh: stagger refresh every 64 ms in a distributed manner | ||
| + | * As oppose to burst refresh (long pause time) | ||
| + | * RAIDR: Reduce DRAM refresh by profiling and binning | ||
| + | * Some row do not have to be refresh very frequently | ||
| + | * Profile the row | ||
| + | * High temperature changes the retention time: need online profiling | ||
| + | * Bloom filter | ||
| + | * Represent set membership | ||
| + | * Approximated | ||
| + | * Can contain false positive | ||
| + | * Better/more hash function helps eliminate this | ||
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| + | |||
buzzword.txt · Last modified: 2015/04/27 18:20 by rachata
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