Willow: A User- Programmable SSD

Transcription

1 Willow: A User- Programmable SSD Sudharsan Seshadri, Mark Gahagan, Sundaram Bhaskaran, Trevor Bunker, Arup De, Yanqin Jin, Yang Liu, and Steven Swanson Non- VolaDle Systems Laboratory Computer Science and Engineering University of California, San Diego 1

2 PCIe- PCM (2010) PCIe- PCM (2015?) Bandwidth Rela;ve to disk x à 2.2x/yr PCIe- Flash (2012) 100 PCIe- Flash (2007) 866à 2.3x/yr 10 Hard Drives (2006) /Latency Rela;ve To Disk

3 Full blown Programmability 3 Case Study: Programmable GPUs Hidden Programmability (Firmware) ParDal Programmability (Shaders)

4 Modern SSDs Hide Their Programmability Fixed interface SATA or NVMe Storage- centric operadons Flexible hardware MulD- core processors Complex firmware Host SATA/NVMe Block Driver CPU Read() Write() SATA/NVMe CPU CPU CPU NV Memory SSD 4

5 5 Candidates for Near-Storage Compute Data- intensive computadon Database scans Transcoding AnalyDcs Data- dependent accesses e.g. pointer chasing SemanDc extension e.g. transacdons Privileged execudon e.g. OS offload Modern SSD processors are inadequate Feasible on modern SSD processors

6 6 [Zhang 12] OS Offload OS Bypass [Caulfield 12] [Caulfield 12] Virtualization Caching [Bhaskaran 13] [Saxena 12] Specialized SSDs [Kang 13] [Coburn 13] [Prabhakaran 08] Transaction Support Query Processing [Do 13] [Kang 13] [Wang 14] [De 13] Key Value Store Novel IO Abstractions [Balakrishnan 12] [Huang 12] [Josephson 10]

7 A Programmable SSD Should Provide a flexible interface New arguments, semandcs, and operadons Programmable in C (or something beher) Enforce file system permissions Allow execudon of untrusted code Allow muldple specialized funcdons to coexist Allow for reuse and sharing of funcdons between applicadons Allow applicadons to invoke operadons without a system call. Be able to run trusted code The OS can delegate operadons to Willow Untrusted applicadons can to invoke them. 7

8 8 Willow System Overview Host Willow Application Custom Kernel Code Willow Driver PCIe Ctrl PCIe ~2 GB/s Bridge Interconnect SPU Trusted Custom Firmware Code Interconnect SPU Trusted Custom Firmware Code Interconnect SPU Trusted Custom Firmware Code 4 GB/s Emulated PCM Emulated PCM Emulated PCM

9 The Willow Processor Complex 125 MHz MIPS processor 32 KB of D- and I- mem A bank of NVM Network interface High- bandwidth Data Streamer MIPS Pipeline SPU 32 KB DMem Streamer Interface 32 KB IMem Interconnect Streamer Emulated PCM 9

10 10 Willow Usage Model and SSD Apps The programmer creates an SSD App The kernel installs SSDApps for applicadons The Willow- resident code A userspace library A kernel module, if needed CommunicaDon via RPCs Host and SSD code can send and receive RPCs Willow CPU SSDApp SSDApp Library Process Kernel App Module Interconnect Interconnect Streamer Willow CPU SSDApp Streamer NVM NVM

11 Trust and Protection A file system sets protecdon policy RPCs carry an unforgeable ProcessID ExecuDon at SPUs is always on behalf of a ProcessID The Willow driver installs access rights Willow firmware checks permissions on access Willow CPU Interconnect Streamer NVM Process Kernel Process Willow CPU Interconnect Streamer NVM 11

12 Willow Case Studies Basic IO Direct IO Caching TransacDon processing Key- Value Store Standard Equipment File Append w/o the file system 12

13 13 TransacDon AcceleraDon with MARS [SOSP 13]

14 Editable Atomic Writes in Willow LogWrite(bufA,addrA,lenA,logAddrA); LogWrite(bufB,addrB,lenB,logAddrB); LogWrite(bufC,addrC,lenC,logAddrC); Commit(); Host Memory Willow A Metadata File B A B C Log File C 14 Data File

15 15 Performance Benefits On TPCB Transac;ons Per Second x ARIES- DirectIO MARS- Willow Thread Count

16 Observations and Limitations SSD App development is reladvely easy Composability of SSD Apps is very valuable Striping data across SPUs increases complexity for some SSD Apps Limited instrucdon and data storage at SPUs is a persistent challenge 16

17 17 The time is ripe for programmable storage Fast NVMs increase storage flexibility and performance demands ExisDng SSDs are already sopware defined Numerous applicadons already exist Willow provides a clean, flexible interface Smooth integradon with exisdng sopware Powerful enough for complex applicadons Preserves file system protecdons Programmable storage can simplify and accelerate applicadons

18 Thanks! 18