FAB: Flash-Aware Buffer Management Policy for Portable Media Players Heeseung Jo, Jeong-Uk Kang, Seon-Yeong Park, Jin-Soo ...
Introduction <ul><li>Portable Media Player (PMP) </li></ul><ul><ul><li>Includes music or video players, digital cameras, P...
Background <ul><li>Flash Memory </li></ul><ul><ul><li>Erase-before-write </li></ul></ul><ul><ul><ul><li>No overwrite, writ...
Flash-Aware Buffer Management <ul><li>System: NAND Flash with DRAM buffer </li></ul><ul><li>Flash-Aware Buffer Management ...
FAB Management, cont’d <ul><li>Victim select strategy </li></ul><ul><ul><li>Block is the replacement unit (erase unit) </l...
Implementation Details <ul><li>Data Structure for FAB </li></ul><ul><ul><li>Block node: LRU linked list </li></ul></ul><ul...
Implementation Details, cont’d <ul><li>Search Operation </li></ul><ul><ul><li>Simple linear search is sufficient: small bu...
Experimental Results <ul><li>Evaluation Methodology </li></ul><ul><ul><li>Default FTL scheme: FAST (fastest) </li></ul></ul>
Experimental Results, cont’d <ul><li>Performance Evaluation </li></ul>GC Write Erase Breakdown Buffer hits
Experimental Results, cont’d <ul><li>The Effect of Buffer Size </li></ul><ul><li>Memory Overhead </li></ul>
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FAB: Flash-Aware Buffer Management Policy for Portable Media ...

  1. 1. FAB: Flash-Aware Buffer Management Policy for Portable Media Players Heeseung Jo, Jeong-Uk Kang, Seon-Yeong Park, Jin-Soo Kim, and Joonwon Lee KAIST IEEE Transactions on Consumer Electronics, 2006 Speaker: Eungkyu Song
  2. 2. Introduction <ul><li>Portable Media Player (PMP) </li></ul><ul><ul><li>Includes music or video players, digital cameras, PDA, cell phone, … </li></ul></ul><ul><ul><li>Flash memory is replacing hard disk for storage </li></ul></ul><ul><li>Buffer Mechanism </li></ul><ul><ul><li>DRAM buffer is also helpful for PMP </li></ul></ul><ul><ul><li>speed and energy consumption, … </li></ul></ul><ul><li>FAB </li></ul><ul><ul><li>LRU is not suitable for PMP nor flash memory </li></ul></ul><ul><ul><li>Minimizes write and erase operations </li></ul></ul><ul><ul><li>Reduces 17% of execution time </li></ul></ul>
  3. 3. Background <ul><li>Flash Memory </li></ul><ul><ul><li>Erase-before-write </li></ul></ul><ul><ul><ul><li>No overwrite, write latency > read, wear-out </li></ul></ul></ul><ul><li>Flash Translation Layer </li></ul><ul><ul><li>Garbage collection: merging log block and its page </li></ul></ul><ul><ul><li>Switch merge </li></ul></ul><ul><ul><ul><li>Garbage collection without write operation </li></ul></ul></ul><ul><ul><ul><li>Optimal case of garbage collection </li></ul></ul></ul><ul><li>This Paper </li></ul><ul><ul><li>Exploit flash memory characteristics without modification of FTL or others </li></ul></ul>
  4. 4. Flash-Aware Buffer Management <ul><li>System: NAND Flash with DRAM buffer </li></ul><ul><li>Flash-Aware Buffer Management Policy </li></ul><ul><ul><li>Access pattern of PMP </li></ul></ul><ul><ul><ul><li>A long sequential access for media data </li></ul></ul></ul><ul><ul><ul><li>Several short accesses for metadata of the file </li></ul></ul></ul><ul><ul><li>Problem of LRU </li></ul></ul><ul><ul><ul><li>Cannot hold short access data </li></ul></ul></ul><ul><ul><ul><li>Long sequential access pushes them away </li></ul></ul></ul><ul><ul><li>Purpose of FAB </li></ul></ul><ul><ul><ul><li>Minimize write and erase operations </li></ul></ul></ul><ul><ul><ul><li>Help to utilize the switch merge </li></ul></ul></ul><ul><ul><ul><li>Maximize overwrite of hot pages  minimize search time </li></ul></ul></ul>
  5. 5. FAB Management, cont’d <ul><li>Victim select strategy </li></ul><ul><ul><li>Block is the replacement unit (erase unit) </li></ul></ul><ul><ul><li>Select the block which has the most pages </li></ul></ul><ul><ul><ul><li>Blocks containing metadata file can survive </li></ul></ul></ul><ul><ul><li>Same # of page  LRU is applied </li></ul></ul><ul><li>Major Advantages </li></ul><ul><ul><li>Reduced write and erase operations </li></ul></ul><ul><ul><ul><li>Different pages with the same block is replaced at once </li></ul></ul></ul><ul><ul><li>Response time: like other caching schemes </li></ul></ul><ul><ul><li>Hot page filtering </li></ul></ul><ul><ul><ul><li>Repetitive writes on the same page are buffered </li></ul></ul></ul>
  6. 6. Implementation Details <ul><li>Data Structure for FAB </li></ul><ul><ul><li>Block node: LRU linked list </li></ul></ul><ul><ul><li>Page node: search tree associated with page number </li></ul></ul>
  7. 7. Implementation Details, cont’d <ul><li>Search Operation </li></ul><ul><ul><li>Simple linear search is sufficient: small buffer size </li></ul></ul><ul><ul><ul><li>Block not found: cache miss – immediately terminates </li></ul></ul></ul><ul><ul><ul><li>Else: continues to search the page node list </li></ul></ul></ul><ul><ul><li>After search, LRU list is rearranged </li></ul></ul><ul><li>Insert Operation: not difficult </li></ul><ul><li>Replace Operation </li></ul><ul><ul><li>Start searching from the tail of the block node list </li></ul></ul><ul><ul><ul><li>Found the block w/ full of page: victim </li></ul></ul></ul><ul><ul><ul><li>Else: block w/ biggest # pages is victim </li></ul></ul></ul><ul><ul><li>Tie: block close to the tail of the list is the victim </li></ul></ul>
  8. 8. Experimental Results <ul><li>Evaluation Methodology </li></ul><ul><ul><li>Default FTL scheme: FAST (fastest) </li></ul></ul>
  9. 9. Experimental Results, cont’d <ul><li>Performance Evaluation </li></ul>GC Write Erase Breakdown Buffer hits
  10. 10. Experimental Results, cont’d <ul><li>The Effect of Buffer Size </li></ul><ul><li>Memory Overhead </li></ul>

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