Analyses of Energy Consumption Changes by Loop Transformations in Log Blocks-based FTL

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Analyses of Energy Consumption Changes by Loop Transformations in Log Blocks-based FTL Memory Architecture and Organization Workshop 2013 (MeAOW 2013) 2013. 10.

1 Analyses of Energy Consumption Changes by Loop Transformations in Log Blocks-based FTL Memory Architecture and Organization Workshop 2013 (MeAOW 2013) Joon-Young Paik*, Tae-Sun Chung**, Eun-Sun Cho*** {lucadi, eschough@cnu.ac.kr*** ; tschung@ajou.ac.kr** *SOftware REsearch Center, Rep. of Korea ***Department of computer technology, Chungnam University, Rep. of Korea **College of Information Technology, Ajou University, Rep. of Korea

2 Outline 3. Energy consumption models loop transformations

large scale storage systems Loop Structures Repetitive execution pattern

4 Flash Memory Ideal replacement for Hard Disk Low power consumption, fast access speed, robustness to shock Widely used from embedded systems to large scale storage systems Loop Structures Repetitive execution pattern Efficient management for the massive data Intensive researches on loop transformations

5 Motivating Example A loop transformation, loop reversal Cause unexpected energy consumption Increase the energy consumption for(i2=0; i2 100;i2++) { for(i1=0; i1 100; i1++) { write(,a[i2][i1],); Loop reversal for(i2=100; i2 0; i2--) { for(i1=100; i1 0; i1--) { write(,a[i2][i1],); Loop A Loop B Goal Analyze how the Affect the energy consumption in flash memory

7 Flash Memory Pages and blocks Asymmetric access speed Asymmetric energy consumption Read Write Erase Access time us/page us/page 1.5 ms/block Energy consumption 4.72 uj/page uj/page uj/block Flash Translation Layer (FTL) Located between file system and flash memory Emulate the block devices by mapping logical addresses into physical addresses Enable file system to be used without any modification

8 EC switch : Energy Consumption of a switch operation EC merge : Energy Consumption of a merge operation EC E : Energy Consumption of an erase operation EC W : Energy Consumption of a write operation N p : The number of pages in a block Block Associative Sector Translation (BAST) A log block-based FTL One log block to one data block property Switch operation EC Switch = EC E Merge operation EC Merge = N p EC w +2 EC E

10 Energy Consumption Model (EC Loop ) No. of requests of write operations EC w +N s EC Switch + N m EC Merge We investigate the values of N s and N m according to the types of a loop EC switch : Energy Consumption of a switch operation EC merge : Energy Consumption of a merge operation E W : Energy Consumption of a write operation N S : No. of switch operations N m : No. of mere operations

11 for(i2=0; i2 MAX2;i2++) { for(i1=0; i1 MAX1; i1++) { write(,a[i2][i1],); for(i1=0; i1 MAX1;i1++) { for(i2=0; i2 MAX2; i2++) { write(,a[i2][i1],); Four Loop Structures Loop Structure I for(i2=max2; i2 0;i2--) { for(i1= MAX1; i1 0; i1--) { write(,a[i2][i1],); Loop Structure II for(i2=0; i2 MAX2;i2++) { for(i1=0; i1 MAX1; i1++) { write(,a[i2][i1],); write(,b[i2][i1],); Loop Structure III Assumption 1) Layout of the array starts from the first page of a block 2) The row-size of the array is larger than a blocks size 3) We restrict stride variables to a block-size. Loop Structure IV

12 Ascending order Outline A[0][3] A[0][2] Log blocks A[1][2] A[1][1] A[2][1] A[2][0] MAX2=2 MAX1=4 A[2][4] Loop Structure I (EC Loop I ) for(i2=0; i2 MAX2;i2++) { for(i1=0; i1 MAX1; i1++) { write(,a[i2][i1],); Access an array in forward order Store the write operations into ascending order Cause switch operations No. of switch operations = log blocks in 0 No. of merge operations 1 A[0][1] A[1][0] A[1][4] A[2][3] A[0][0] A[0][4] A[1][3] A[2][2]

13 Descending order Outline 5. Experiments Log blocks MAX2=2 MAX1=4 Loop Structure II (EC Loop II ) for(i2=max2; i2 0;i2--) { for(i1= MAX1; i1 0; i1--) { write(,a[i2][i1],); Access an array in backward order Store the write operations into descending order Cause merge operations log blocks in A[2][1] A[2][2] A[2][3] A[1][2] A[1][3] A[1][4] A[0][3] A[0][4] A[1][0] A[0][0] A[0][1] No. of switch operations = 0 No. of merge operations = A[2][4] A[2][0] A[1][1] A[0][2]

14 MAX2=2 MAX1=4 Loop Structure III for(i1=0; i1 MAX1;i1++) { for(i2=0; i2 MAX2; i2++) { write(,a[i2][i1],); Access the elements across different rows, and re-access the rows Due to the re-use pattern, the energy consumption of Loop Structure III is sensitive to the size of the log blocks : EC Loop III and EC Loop III N

15 Ascending order Non-ascending order Outline Loop Structure III (EC Loop III ) : Sufficient log blocks Ascending order occurs log blocks A log block has only one row Non-ascending order occurs A log block has more than two log blocks A[0][3] A[0][4] A[1][4] A[0][2] A[1][2] A[1][3] A[2][4] A[0][1] A[1][1] A[2][1] A[2][3] A[0][0] A[1][0] A[2][0] A[2][2] 1 No. of switch operations MAX 2+1 MAX No. of merge operations

Loop Structure III (EC Loop III N ) : Insufficient log blocks The log blocks are evicted by the replacement scheme before the log blocks are re-used MAX 2 + 1 MAX 1 + 1 log blocks are evicted, each

16 Loop Structure III (EC Loop III N ) : Insufficient log blocks The log blocks are evicted by the replacement scheme before the log blocks are re-used MAX MAX log blocks are evicted, each of which cause a merge operation A[2][0] is written MAX2=2 MAX1=4 A[0][0] A[1][0] 1. The log block that has A[0][0] is evict. 2. The evict log block causes a merge operation 3. A[2][0] is stored into the log block. A[2][0] A[1][0] Evicted log block New log block A[2][0] No. of switch operations = 0 No. of merge operations = MAX MAX 1 + 1

17 MAX2=2 MAX1=4 Loop Structure IV (EC Loop IV ) for(i2=0; i2 MAX2;i2++) { for(i1=0; i1 MAX1; i1++) { write(,a[i2][i1],); write(,b[i2][i1],); Access the elements of two arrays in turn, in which each array is referenced in forward order Store the write operations into log blocks in ascending order Due to the one log block to one data block property No. of switch operations = 2 MAX 2+1 MAX No. of merge operations 2

18 consumption changes by Loop Reversal Loop Interchange Loop Distribution

19 consumption changes by loop transformations based on models Loop Reversal Transform Loop I into Loop II Cost model: EC Loop I EC Loop II N s Loop I Loop II Cp. N m [0,1] Transform Loop II into Loop I 0 Cost model: EC Loop II EC Loop I Loop II Loop I Cp. N s 0 N m [0,1]

20 consumption changes by loop transformations based on models Loop Interchange: the log blocks are fully enough Transform Loop I into Loop III Cost model: EC Loop I EC Loop III N s Loop I Loop III Cp. [1, N m [0,1] [0, Transform Loop III into Loop I ], ], Cost model: EC Loop III EC Loop I Loop III Loop I Cp. N s [1, N m [0, ], ] [0,1],

21 consumption changes by loop transformations based on models Loop Interchange: the log blocks are not enough for the Loop Structure III Transform Loop I into Loop III Cost model: EC Loop I EC Loop III N Loop III Loop I Cp. N s 0 N m MAX MAX [0,1] Transform Loop III into Loop I Cost model: EC Loop III N EC Loop I Loop I Loop II Cp. N s 0 N m [0,1] MAX MAX 1 + 1

22 consumption changes by loop transformations based on models Loop Distribution Transform Loop IV into a couple of Loop I Cost model: EC Loop IV 2 EC Loop I Loop IV A couple of Loop I Cp. N s 2 MAX 2+1 MAX MAX 2+1 MAX 1 +1 N m [0,2] [0,2]

04 uj Energy consumption of a erase operation: 572.

Transformed loop Evaluation in Energy Consumption uj uj Loop I

III Loop I <Loop interchange: Log blocks are insufficient> uj

24 BAST simulator No. of log blocks: 32 Energy consumption of a write operation: uj Energy consumption of a erase operation: uj MAX2=100 MAX1=100 i2 = 1 i1 = 1 : Original loop : Transformed loop Evaluation in Energy Consumption uj uj Loop I Loop II Loop II Loop I <Loop reversal> Loop I Loop III Loop III Loop I <Loop interchange: Log blocks are insufficient> uj Loop I Loop III Loop III Loop I <Loop interchange: Log blocks are sufficient> uj Loop IV A couple of Loop I <Loop distribution>

26 Energy Consumption Based on flash memory properties and loop structures Energy Consumption Effect of Loop transformations Analyses on changes in energy consumption by based on the proposed energy consumption models Future Works Energy Consumption in Full Associative Sector Translation (FAST)

27 Q & A

data block data block log block log block group 0 group 1 group 0 group 1

data block data block log block log block group 0 group 1 group 0 group 1 US008261010B2 (12) Unlted States Patent (10) Patent N0.2 US 8,261,010 B2 Eom et al. (45) Date of Patent: Sep. 4, 2012 (54) METHODS FOR DISTRIBUTING LOG (56) References Cited BLOCK ASSOCIATIVITY FOR REAL-TIME