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NVDIMM block drivers with NFIT


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NVDIMM block drivers with NFIT

  1. 1. NVDIMM block drivers with NFIT March, 2016, SUSE Labs Taipei technology sharing day, Taipei Joey Lee SUSE Labs Taipei
  2. 2. 2 Agenda • NVDIMM • NFIT • Conceptual model ‒ nvdimm.txt ‒ Namespace/Region ‒ PMEM ‒ BLK ‒ NFIT ‒ BTT • Q&A
  3. 3. NVDIMM
  4. 4. 4 NVDIMM • NVDIMM: Non-Volatile DIMM. Non-volatile memory in a DIMM form factor. [1] ap-several-routes/
  5. 5. 5 NVDIMM Architecture
  6. 6. 6 NVDIMM Architecture - Block
  7. 7. 7 SPA/DPA • SPA: System Physical Address. A physical address on the host operating system. [1] • DPA: DIMM Physical Address. An address within the memory in an NVDIMM. [1]
  8. 8. 8 SPA/DPA NVDIMM Namespace Specification, Intel
  9. 9. 9 SPA/DPA Interleave • DPA: DIMM Physical Address, is a DIMM-relative offset. With one DIMM in the system there would be a 1:1 system-physical-address:DPA association. Once more DIMMs are added an memory controller interleave must be decoded to determine the DPA associated with a given system-physical-address. BLK capacity always has a 1:1 relationship with a single-dimm's DPA range. [2]
  10. 10. 10 SPA/DPA Interleave NVDIMM Namespace Specification, Intel
  11. 11. 11 PMEM • Persistent Memory (or PMEM): Byte‐addressable memory which retains its contents across power loss.A DIMM primarily containing non‐volatile memory. [3] • PMEM: A system physical address range where writes are persistent. A block device composed of PMEM is capable of DAX. A PMEM address range may span/interleave several DIMMs. [2] • DAX: File system extensions to bypass the page cache and block layer to mmap persistent memory, from a PMEM block device, directly into a process address space. [2]
  12. 12. 12 Block Window • BW(Block Window): A set of registers consisting of a command register, a status register, and an aperture allowing the NVDIMM driver to read and write blocks of data to any persistent area on an NVDIMM. [1] • BLK: A set of one or more programmable memory mapped apertures provided by a DIMM to access its media. This indirection precludes the performance benefit of interleaving, but enables DIMM-bounded failure modes. [2]
  13. 13. 13 Block Window
  14. 14. 14 BTT • Block Translation Table. A software data structure, defined in the NVDIMM Namespace Specification, which prevents torn blocks when a write is interrupted by a system crash, hang, or power failure. [1] • BTT: Existing software may have an expectation that the power-fail-atomicity of writes is at least one sector, 512 bytes. The BTT is an indirection table with atomic update semantics to front a PMEM/BLK block device driver and present arbitrary atomic sector sizes. [2]
  15. 15. 15 Namespace • NVDIMM Namespace: Similar to an NVMe Namespace or a Logical Unit (LUN) on a SCSI disk, this is a software mechanism for managing ranges of persistence on NVDIMMs. [1] • NVDIMM Namespace Label: Labels, stored at a known location on NVDIMMs, that define the DIMM’s contribution to NVDIMM Namespaces. This is a software mechanism; the DIMM itself just sees the labels as part of the overall data stored on the DIMM. [1]
  16. 16. 16 PMEM Namespace NVDIMM Namespace Specification, Intel
  17. 17. 17 BLK Namespace NVDIMM Namespace Specification, Intel
  18. 18. 18 Namespace NVDIMM Namespace Specification, Intel
  19. 19. 19 I/O on Multi-Range BLK Namspaces NVDIMM Namespace Specification, Intel
  20. 20. 20 Example Software Organization for Block I/O NVDIMM Namespace Specification, Intel
  21. 21. 21 Example Software Organization for Namespace Management NVDIMM Namespace Specification, Intel
  22. 22. NFIT
  23. 23. 23 NFIT • NFIT: The NVDIMM Firmware Interface Table, which defines the ACPI-like information created by the BIOS to inform the OS about NVDIMMs in the system. [1] • Device Specific Method (DSM): The NVDIMM root device and the NVDIMM devices can have device specific methods (_DSM) to provide additional functions specific to a particular NVDIMM implementation. [4]
  24. 24. 24 NFIT Overview ACPI 6.0 spec
  25. 25. 25 NFIT NVDIMM Block Window Driver Writer’s Guide, Intel
  26. 26. 26 NFIT Information NVDIMM Block Window Driver Writer’s Guide, Intel
  27. 27. 27 NFIT SPA NVDIMM Block Window Driver Writer’s Guide, Intel
  28. 28. 28 NFIT Flush Hint NVDIMM Block Window Driver Writer’s Guide, Intel
  29. 29. 29 NFIT Block Window NVDIMM Block Window Driver Writer’s Guide, Intel
  30. 30. 30 NFIT (fixed) NVDIMM Block Window Driver Writer’s Guide, Intel
  31. 31. Conceptual model
  32. 32. 32 Conceptual model of nvdimm.txt
  33. 33. 33 Conceptual model of driver/nvdimm/namsepace, region
  34. 34. 34 Conceptual model of driver/nvdimm/pmem
  35. 35. 35 Conceptual model of driver/nvdimm/blk
  36. 36. 36 Conceptual model of driver/nvdimm/btt
  37. 37. 37 Conceptual model of driver/acpi/nfit
  38. 38. Q&A
  39. 39. 39 Reference • [1] NVDIMM Block Window Driver Writer’s Guide, Intel • [2] Documentation/nvdimm/nvdimm.txt, Linux Kernel • [3] NVDIMM Namespace Specification, Intel • [4] NVDIMM DSM Interface Example, Intel
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