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FlatFlash : Exploiting the Byte-Accessibility of SSDs Within A Unified Memory-Storage Hierarchy Ahmed Abulila 1 , Vikram Sharma Mailthody 1 , Zaid Qureshi 2 , Jian Huang 1 , Nam Sung Kim 1 , Jinjun Xiong 3 , Wen-mei Hwu 1 1 ECE, 2 CS, University of Illinois at Urbana-Champaign, Urbana, IL 61801 3 Cognitive Computing & University Partnership, IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598 Storage Session: 11:30 AM on Wednesday 17 th April 2019 mmap() munmap() msync() File Virtual Memory Application File System SSD OS File System Application SSD Virtual Memory Stalls the process DRAM thrashing/pollution High I/O TraΠc Page-level persistency Block Interface DRAM in SSD PCIe MMIO Cache Coherence Page Promotion to Host DRAM Off-Critical Path Page Promotion In-Flight Promotion with Cache-Line Granularity Set Bits in Promotion Look-aside Buffer Handle Data Access Conflict Cache Host Bridge Promotion Lookaside Buffer SSD SSD-Cache CPU flush cache lines: clflush/clwb verify addr & disable promotion PCIe write-verify read ❶ ❷ ❸ FlatFlash disables page promotion for persistent memory regions create_pmem_region (void* vaddr, size_t size) Scalable Logging for Database SSD Centralized Log Buffer TX A TX B TX C Lock Contention SSD Log Log Log TX A TX B TX C (a) Logging with block I/O (b) Logging with FlatFlash Metadata Durability in File Systems root pointer block pointer block inodes data block metadata structure packed in blocks Put It All Together Byte-accessibility with PCIe MMIO + OpenCAPI Unified Memory Space Adaptive Page Promotion Byte-Granular Data Persistency Paper Download Results Ensuring Data-Consistency During Page Promotion Enabling Byte-Granular Data Persistence System Implications of FlatFlash Using Flash as Non-Volatile Memory Limitations of Block I/O Interface Enabling the Byte-Accessibility of SSDs Unifying the Memory and Storage Performance Challenges
