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Processor Support for NVM Programming

Andy Rudoff Intel Corporation NVM Summit January 20th 2015

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NVM Summit

Challenges Introduced by NVM Programming

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NVM Summit 3

NVDIMM

User Space

Kernel Space

Standard File API

NVDIMM Driver

Application

File System

Application Application

Standard Raw Device

Access

Block File Memory

Load/Store

Management Library

Management UI

Standard File API

Mgmt.

PM-Aware File System

MMU Mappings

NVM Summit

Where Writes are Cached

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NVDIMM

User Space

Kernel Space

Application

Load/Store Standard File API

PM-Aware File System

MMU Mappings

No Page Cache

msync() FlushViewOfFile()

pmem_persist()

NVM Summit

The Road to Persistence

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Core

L1 L1

L2

L3

Core

L1 L1

L2

Core

L1 L1

L2

Core

L1 L1

L2

NVDIMM NVDIMM

NVDIMM NVDIMM

Memory Controller Memory Controller

MOV

NVM Summit

Hiding Places

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Core

L1 L1

L2

L3

Core

L1 L1

L2

Core

L1 L1

L2

Core

L1 L1

L2

NVDIMM NVDIMM

NVDIMM NVDIMM

Memory Controller Memory Controller

MOV

NVM Summit

Instruction-Level Support

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NVM Summit

Two Levels of Flushing Writes

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NVDIMM NVDIMM

CLFLUSH, CLFLUSHOPT, CLWB

PCOMMIT

NVM Summit

Flushing Writes from Caches

Instruction Meaning

CLFLUSH addr Cache Line Flush: Available for a long time

CLFLUSHOPT addr Optimized Cache Line Flush: New to allow concurrency

CLWB addr Cache Line Write Back: Leave value in cache

for performance of next access

WBINVD Heavy Hammer:

used by OS to flush entire cache Privileged

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NVM Summit

Flushing Writes from Memory Controller

Instruction Meaning

PCOMMIT Persistent Commit:

Flush stores accepted by memory subsystem

Asynchronous DRAM Refresh Flush outstanding writes

on power failure Platform-Specific Feature

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NVM Summit

How to Use This

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NVM Summit

NVM Library: pmem.io 64-bit Linux Initially

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NVDIMM

User Space

Kernel Space

Application

Load/Store Standard File API

PM-Aware File System

MMU Mappings

Library

• Open Source • http://pmem.io

• Libpmem • Libpmemobj • Libpmemblk • Libpmemlog • Libvmem

Transactional

NVM Summit

Summary

• New Instructions Emerging – Support the SNIA NVM Programming Model

• Stay Tuned… more to come…

– But you probably want to use a library: http://pmem.io

• Intel Architecture Instruction Set Extensions Programming Reference – https://software.intel.com/en-us/intel-isa-extensions

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NVM Summit 14