NVRAM for the computer scientist
Kevin Marquet
INSA Lyon / CITI Lab / INRIA Socrate
March 20th, 2015
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A computer
CPU
DRAM
Disk
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A computer
CPU
DRAM
Access time : 50ns
Loose data when not powered
Disk
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A computer
CPU
DRAM
Disk
Access time : 50ns
Loose data when not powered
Access time : 100000 ns
Retains data when not powered
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NVRAMs
Read/Write times, scalability, density, energy consumption
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NVRAMs
Read/Write times, scalability, density, energy consumption
PCM
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Read time : 100ns
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Write time : 200ns
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NVRAMs
Read/Write times, scalability, density, energy consumption
MRAM
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Read time : 10ns
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Write time : 20ns
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NVRAM for mass storage
CPU
DRAM
Disk
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NVRAM for mass storage
CPU
DRAM
NVRAM
Disk
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NVRAM for mass storage
CPU
DRAM
NVRAM
Disk
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Dedicated file systems
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Database in NVRAM
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DRAM + NVRAM
CPU
DRAM
Disk
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DRAM + NVRAM
CPU
NVRAM
DRAM
Disk
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DRAM + NVRAM
CPU
NVRAM
DRAM
Disk
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DRAM + PCM : More RAM
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DRAM + PCM :
wear-Leveling
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...
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Architecture
CPU
DRAM
Disk
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Architecture
L1 Cache
CPU
L2 Cache
DRAM
Disk
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Architecture
L1 Cache
CPU
L2 Cache
DRAM
Disk
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4x more, 2x slower ?
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L1 ? L2 ? L3 ?
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Several technologies ?
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NVRAM as working memory
CPU
DRAM
Disk
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NVRAM as working memory
CPU
NVRAM
DRAM
Disk
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NVRAM as working memory
CPU
NVRAM
DRAM
Disk
Existing works with PCM :
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Endurance problem
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Performance w.r.t. DRAM
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Energy consumption increases
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NVRAM as the only memory
CPU
DRAM
Disk
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NVRAM as the only memory
CPU
DRAM
NVRAM
Disk
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NVRAM as the only memory
CPU
DRAM
NVRAM
Disk
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Impact on the implementation (Harvard/Von Neumann
architecture)
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Operating system
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Paging...
Frame n
Page table
(in RAM)
Virtual
address
CPU
...
Physical
address
Frame 5
Frame 4
MMU
Frame 3
Frame 2
Frame 1
TLB
Frame 0
DRAM
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Operating system
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Paging...
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...vs. file system
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Operating system : boot and reboot ?
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Installation and launch
CPU
DRAM
Disk
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Operating system : boot and reboot ?
I
Installation and launch
CPU
DRAM
Disk
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Operating system : boot and reboot ?
I
Installation and launch
CPU
DRAM
Disk
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Operating system : boot and reboot ?
I
Installation and launch
CPU
DRAM
NVRAM
Disk
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Operating system : boot and reboot ?
I
Installation and launch
CPU
DRAM
NVRAM
Disk
I
No reboot...
I
I
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bug ?
reset ? Checkpoint ?
Compilation
I
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produce new executable files
decides when to checkpoint ?
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Programming model
I
With DRAM + Disk : decide what is persistent
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With NVRAM : decide what is non-persistent
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Peripherals
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Glory ?
Test my ideas, publish, be famous
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Glory ?
?
Test my ideas, publish, be famous
Buy a computer that includes MRAM
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Glory ?
?
Test my ideas, publish, be famous
Buy a computer that includes MRAM
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Simulation ;-(
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Simulation ;-(
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Not so bad
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Simulation ;-(
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Not so bad
I
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Explore memory hierarchies
Feedback to architects
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Extrapolate from dram accesses : No !
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Emulate : yes (but not so easy)
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Which technology ?
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Which technology is realistic ?
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Understand the technology
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Which technology ?
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Which technology is realistic ?
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Understand the technology
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What about us ?
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Internet of Things
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Energy harvesting
Capacitor voltage (V)
3.5
3.0
2.5
2.0
Init
5000
5200
No chkpt
5400
5600
Chkpt success
5800
Time (ms)
6000
Restore
6200
6400
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Why now ?
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Because architects will (again) design CPUs impossible to
program
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...or we can help design these CPUs
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Lots of recent works
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Real platform appeared recently
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Conclusion
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Can lead to huge changes in computer science
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Simulation necessary, for now
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Feedback to architects
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Memory hierarchy depends on the use case
Which technology is viable ?
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Always in motion the future is...
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Credits
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Bibliography : kevinmarquet.net/research/nvram
Pictures :
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Small bib: andrebourgeois.fr/ImageBibliotheque.JPG
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Big bib : www.10escadron.com/bibliotheque/
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Mram: ndl.hanyang.ac.kr/xe/files/attach/images/79/790/001/10.png
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Javacard:
javacard.vetilles.com/wp-content/uploads/2008/09/gemalto-jc3.jpg
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Rolex: blog.titanblack.co.uk/wp-content/uploads/2013/04/
Platinum-Rolex-Daytona-Basel-2013.jpg
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Files :
nixlinux.com/wp-content/uploads/2014/04/61tdpgruLeL._SL1500_.jpg
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Elf: www.johnloomis.org/microchip/pic32/elf/Elf-layout.png
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Key: http://www.businesshi-lite.co.za/wp-content/uploads/2012/06/
key-small-1024x768.jpg
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Sensor: www.libelium.com/libelium-images/generico/waspmote_
radiation_sensor_board-1000.png
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Wislab: wislab.cz/media/content-images/WislabNode-S-description.png
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Simulation: www.mpg.de/698541/standard.jpeg
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Backup : fetch-decode-execute
Decode
Fetch
Execute
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