1. OS frontiers in the AI era
Felix Xiaozhu Lin
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2. Who Am I
• Fall 2020. Assoc. Prof, UVA CS – Looking forward to it!
• 2014 – 2020. Asst. Prof, Purdue ECE
• 2014 PhD in CS. Rice
• 2008 MS + BS. Tsinghua
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3. What is an OS?
Undergrads (Some) data scientists Tech media
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Are these OSes?

4. the era of AI!
Where are
we today?
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https://en.wikipedia.org/wiki/Time_(xkcd)#/media/File:Xkcd_time_frame_0001.png

5. The 3rd boom of AI
1960s 1970s 1980s 1990s 2000s 2010s 2020s
Classical AI Expert systems Machine learning
Ups
Downs
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6. Two Pendulums
1960s 1970s 1980s 1990s 2000s 2010s 2020s
Expert systems Machine learning
Ups
Downs
Centralized
Decentralized
Dedicated
hw & net
PC + Internet
Datacenters
Cloud computing
5G, edge,
embedded AI…
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Classical AI

7. Two Pendulums
1960s 1970s 1980s 1990s 2000s 2010s 2020s
Expert systems Machine learning
Generalized
Specialized
Microcomputers,
x86, DBMS, PC
Mainframes,
Apollo11
Ups
Downs
Wearables/IoT,
NoSQL, GPU/FPGA, RISCV
Centralized
Decentralized
Dedicated
hw & net
PC + Internet
Datacenters
Cloud computing
5G, edge,
embedded AI…
8
Classical AI

8. Two Pendulums
1960s 1970s 1980s 1990s 2000s 2010s 2020s
Expert systems Machine learning
Generalized
Specialized
Microcomputers,
x86, DBMS, PC
Mainframes,
Apollo11
Ups
Downs
Wearables/IoT,
NoSQL, GPU/FPGA, RISCV
Centralized
Decentralized
Dedicated
hw & net
PC + Internet
Datacenters
Cloud computing
5G, edge,
embedded AI…
9
Classical AI

9. My view of OS
OS == System Software == Software Infrastructure
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10. What you have learnt from undergrad OS class
1960s 1970s 1980s 1990s 2000s 2010s 2020s
GOFAI Expert systems Machine
learning
Generalized
Specialized
Microcomputers,
x86, DBMS, PC
Mainframes,
Apollo11
Ups
Downs
Wearables/IoT,
NoSQL, GPU/FPGA, RISCV
Centralized
Decentraliz
ed
Dedicated
hw & net
PC + Internet
Datacenters
Cloud
computing
5G, edge,
embedded AI…
14

11. What OS people are working on
1960s 1970s 1980s 1990s 2000s 2010s 2020s
GOFAI Expert systems Machine
learning
Generalized
Specialized
Microcomputers,
x86, DBMS, PC
Mainframes,
Apollo11
Ups
Downs
Wearables/IoT,
NoSQL, GPU/FPGA, RISCV
Centralized
Decentraliz
ed
Dedicated
hw & net
PC + Internet
Datacenters
Cloud
computing
5G, edge,
embedded AI…
15

12. So, where are
we today?
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13. • Diverse
• A few common OSes
• Many specialized ones
• Serving “things” in addition to humans
• Defined by scenarios
• Generic OSes  firmware
• Specialized OSes  overlays
• Blurry boundaries
• arch, runtime, compiler, kernel,
hypervisor, trusted exec environment…
Cloud
Edge
Devices
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14. Three flavors of OS research
1. Tune up
2. Do a specific thing well
3. Show possibility
Common themes:
open blackboxes,
break, & build
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15. Case 1: A highspeed stream
analytics engine
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16. High‐throughput. Sub‐second delay.
Timely processing before data gets cold! 22
“Hot springs”: telemetry events
Power sensor
140M events/day
Oil rig
1‐2TB/day
Manufacturing machines
PBs/day

17. Stream analytics: state of the art
• Classic engines?
• StreamBase, Aurora, TelegraphCQ, NiagaraST…
• Single threaded. Not scaling well.
• Modern engines for datacenters?
• Apache Flink, Spark Streaming, Beam…
• Designed for tens ‐ hundreds of machines. Scaling out.
• Assuming okay if individual nodes perform poorly
• As analytics moves to the edge  bad
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18. Project StreamBox
stream analytics at the memory speed
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• RDMA
• Co‐designed with
mm/scheduling
• RDMA
• Co‐designed with
mm/scheduling
Stream pipeline Threads
Ingestion
Scheduler
Mem
• Squeeze parallelism for
multi/manycore
• Manage NUMA domains
• Squeeze parallelism for
multi/manycore
• Manage NUMA domains
Exploit high‐bandwidth memoryExploit high‐bandwidth memory
[ASPLOS'19] "StreamBox‐HBM: Stream Analytics on High Bandwidth Hybrid Memory," Hongyu Miao, Myeongjae Jeon, Gennady Pekhimenko,
Kathryn S. McKinley, and Felix Xiaozhu Lin
[USENIX ATC'17] "StreamBox: Modern Stream Processing on a Multicore Machine," Hongyu Miao, Heejin Park, Myeongjae Jeon, Gennady
Pekhimenko, Kathryn S. McKinley, and Felix Xiaozhu Lin, in Proc. USENIX Annual Technical Conference, 2017.
[ASPLOS'16] "memif: Towards Programming Heterogeneous Memory Asynchronously," Felix Xiaozhu Lin and Xu Liu, in Proc. ACM Int. Conf.
Architectural Support for Programming Languages and Operating Systems, 2016.

19. CoresCores
High‐bandwidth hybrid memory
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3D DRAM Normal DRAM
Tradeoffs: capacity vs. bandwidth
Untraditional memory hierarchy
No latency benefit
Unlike SRAM+DRAM
16 GB
375 GB/s
~100 GB
~100 GB/s

20. 26
Already on off‐the‐shelf machinesIntel Xeon Phi Knights Landing (KNL)

21. 27
HBM
CoresCores
Normal DRAM
Streaming
data
Data Bundles
Index
{key, pointer}
Capacity: Use HBM only for grouping indexes

22. 28
Cheap VM
(huge page)
Apps
OS
kernel
Fast net stack
(40 GbE or RDMA)
High task
parallelism
Custom mem
allocator
Sequential mem
access
Runtime
Thread pool
+ custom task scheduler
Wide SIMD
(avx512)
Hybrid
memory
A system software’s approach to 3D DRAM
Blurry boundaries

23. Case 2: Autonomous AI on
Cameras
[MobiSys'20] "Approximate Query Processing on Autonomous Cameras," Mengwei Xu, Xiwen Zhang, Yunxin Liu,
Xuanzhe Liu, and Felix Xiaozhu Lin 29

24. X1Video: a killer AI application
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25. 31

26. 32

27. 33
Cut the cords

28. Run on harvested energy
Solar
Wind
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29. 35
… and on wireless

30. Construction sites Farms
Boats/RVs Warehouses
Photos Credits: Reolink
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Pervasive cameras

31. Object
Counts
Elf
Running analytics on wire‐free
cameras?
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32. Query: (car, 30 mins)
Install
7:00AM-7:30AM [500 + 100] Cars
7:30AM-8:00AM [700 + 140] Cars
8:00AM-8:30AM [800 + 180] Cars
8:30AM-9:00AM [400 + 100] Cars
9:30AM-10:00AM [200 + 80] Cars
Sample &
capture
200‐80 +80
Elf: Query model
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33. Camera Operating System
Planning Energy via
Reinforcement Learning
Planning Energy via
Reinforcement Learning
Sampled frames
Aggregator
with error
Integration
Aggregator
with error
Integration
Selected NeuralNet
Object
counts
Elf: System Internals
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34. Elf prototype: heterogeneous processors
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35. 7:00AM-7:30AM [500 + 100] Cars
7:30AM-8:00AM [700 + 140] Cars
8:00AM-8:30AM [800 + 180] Cars
8:30AM-9:00AM [400 + 100] Cars
9:30AM-10:00AM [200 + 80] Cars
Ground
Truth
Error:
11%
Confidence interval width: 17%
Auburn, AL
Hampton, NY Jackson, WY
Taipei Taipei
~1000 hours
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36. M4
AUTONOMOUS
Intelligence
OS for AI + AI for OS
= Autonomous infrastructure
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37. Case 3: Kernel IO on co‐processors
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38. 44

39. 45
Weak co‐processors

40. 46
CPU Co
Proc
2.5GHz 50MHz
DRAM IO
A heterogeneous SoC

41. 47
CPU Co
Proc
2.5GHz 50MHz
DRAM IO
Weak co‐processors: suits low‐power IO tasks!
high
efficiency
Linux Kernel
IO
tasks

42. 48
CPU Co
Proc
2.5GHz 50MHz
DRAM IO
Kernel execution on weak co‐processors?
Linux Kernel
IO
tasks
Diff ISA
No MMU
…

43. 49
CPU Co
Proc
DRAM IO
Co‐processor translates unmodified kernel binary
Dynamic
Binary
Translation
Linux Kernel
IO
tasks
[USENIX ATC 19] "Transkernel: An Executor for Commodity Kernels on Peripheral Cores,"
Liwei Guo, Shuang Zhai, Yi Qiao, and Felix Xiaozhu Lin

44. Take away:
• Taming an OS kernel (a beast) for new hardware
• … without re‐engineering much of the software stack
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45. Recap
• What are OSes in 2020?
• Three OS projects:
• spanning IoT, mobile, and datacenters
• each with different flavors
• The builder culture
• open blackboxes
• break things
• build things from the ground up
• Started by a small group of hardcore hackers
• Now more diverse and inclusive
• A brave new world
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StreamBox
Elf

46. Image credits
• https://dsportmag.com/the‐tech/test‐n‐tune/test‐tune‐2017‐subaru‐wrx‐
sti‐part3‐closer‐to‐the‐ej257s‐limits/
• https://techcrunch.com/2009/11/19/redneck‐rampage‐a‐truck‐with‐a‐jet‐
engine/?utm_source=feedburner#038;utm_medium=email
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