Outline Introduction Integrating PCM into the Memory hierarchy PCM for main memory PCM for auxiliary memory Conclusion
Outline • Introduction • Integrating PCM into the Memory Hierarchy − PCM for main memory − PCM for auxiliary memory • Conclusion
Integrating PCM into the memory hierarchy PCM for main memory Replacing dram with PCm to achieve larger main memory capacity PCM for auxiliary memory PCM as a write buffer for HDd/SSD DISK Buffering dirty page to minimize the disk write l / os PCM as secondary storage Storing log records
Integrating PCM into the Memory Hierarchy • PCM for main memory – Replacing DRAM with PCM to achieve larger main memory capacity • PCM for auxiliary memory – PCM as a write buffer for HDD/SSD DISK Buffering dirty page to minimize the disk write I/Os – PCM as secondary storage Storing log records
[ISCA09] PCM for main memory (DAc'o9j CCD’11 [CIDR'1 CPU CPU CPU L1/L2 Cache L1/L2 Cache L1/L2 Cache Memory Controller Memory Controller Memory Controller DRAM Cache Write buffer Phase Change Memory Phase Change Memory Phase Change Memory HDD/SSD Disk HDD/SSD Disk HDD/SSD Disk (a PCM-only memory (b DRAM as a cache memory cDRAM as a write buffer
PCM for main memory Phase Change Memory Memory Controller HDD/SSD Disk CPU L1/L2 Cache (a)PCM-only memory Phase Change Memory Memory Controller HDD/SSD Disk CPU L1/L2 Cache DRAM Cache (b)DRAM as a cache memory Phase Change Memory Memory Controller HDD/SSD Disk CPU L1/L2 Cache DRAM Write buffer (c)DRAM as a write buffer [ISCA’09] [ICCD’11] [DAC’09] [CIDR’11]
PCM for main memory Challenges with PCM Major disadvantage -Writes Compared to read operation PCm writes incur higher energy consumption higher latency and limited endurance Read latency 20 50ns Write latency lus Read energy 1 J/GB Write energy 6J/GB Endurance 1056~108 Reducing PCM writes is an important goal of data management on PCM!
PCM for main memory Challenges with PCM • Major disadvantage – Writes Compared to read operation ,PCM writes incur higher energy consumption、 higher latency and limited endurance Read latency 20~50ns Write latency ~1us Read energy 1 J/GB Write energy 6 J/GB Endurance 106~108 Reducing PCM writes is an important goal of data management on PCM !
PCM for main memory IiSCAs'O7 [ISCA09 Optimization on pCm write [MICRO09 Optimization data comparison write Goal: write only modified bits rather than entire cache line Approach: read-compare-write CPU cache010110000110101 0 0110 01|101110 rea PCM po1o1oaao1o1叫1
• Optimization: data comparison write • Goal: write only modified bits rather than entire cache line • Approach: read-compare-write 0 1 0 1 1 0 1 1 0 1 1 0 1 1 1 0 0 1 0 1 1 0 10 10 0 1 1 0 1 10 1 01 0 1 0 1 1 0 1 1 0 1 1 0 1 1 1 0 0 1 0 1 1 0 0 0 0 1 1 0 1 0 1 1 CPU cache PCM PCM for main memory Optimization on PCM write [ISCAS’07] [ISCA’09] [MICRO’09] read