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BTLab Embedded Virtualization Group Outline  Introduction  Performance Analysis  PerformanceTuning Methods  Experimental Results  Conclusion 2

BTLab Embedded Virtualization Group Outline  Introduction  Performance Analysis  PerformanceTuning Methods  Experimental Results  Conclusion 3

BTLab Embedded Virtualization Group Virtualization in General  A host(VMM, Virtual Machine Monitor) manages the hardware resources Multiplexing or Partitioning  Virtualization Flavors Full virtualization Paravirtualization  Virtualization Application Server Desktop Embedded System OS App Hardware Guest OS App Guest OS App Host(VMM) Hardware 4

BTLab Embedded Virtualization Group Motivation 5  RTOS is primitive, simple executives Task scheduling Interrupt Handling  RT applications now require TCP/IP&GUI File system&Database Multi-core support  Classic solutions Add these non-RT services to the basic RT kernel Add RT extension to the general-purpose kernel Task scheduling Kernel preemptivity

BTLab Embedded Virtualization Group System Consolidation  Multi-core enablement for legacy embedded uni- processor applications 6

BTLab Embedded Virtualization Group Another Solution  Deploy separate RTOS and GPOS on single embedded platform RTOS: real-time tasks GPOS: non-real-time services  Meet increasing RT application requirements while enjoying all the benefits of embedded virtualization  Add RT extension to the VMM VM scheduling VMM kernel preemptivity 7

BTLab Embedded Virtualization Group Embedded Real-Time Architecture 8  Multi-core CPU with virtualization extension  KVM as the hypervisor  Linux as the GPOS  VxWorks as the RTOS

BTLab Embedded Virtualization Group Outline  Introduction  Performance Analysis  PerformanceTuning Methods  Experimental Results  Conclusion 9

BTLab Embedded Virtualization Group PDLT: Process Dispatch Latency Time  Between an interrupt occurs and the first command of a process that has been awakened by the interrupt service routine longest antency are on the order of tens up to hundreds of milliseconds 10

BTLab Embedded Virtualization Group  Six stages associated with the delivery of the interrupt to the guest OS  System load causing additional latency Computational loads Interrupt loads Virtualization-Caused Latency 11

BTLab Embedded Virtualization Group Outline  Introduction  Performance Analysis  PerformanceTuning Methods  Experimental Results  Conclusion 12

BTLab Embedded Virtualization Group Prioritization  A straightforward approach to improving guest responsiveness over QEMU/KVM is to raise the priorities of QEMU’s threads and lift them into a real-time scheduling class  Approaches Shell command: chrt System Call: sched_setscheduler() 13

BTLab Embedded Virtualization Group Dedicated Core  Reserve one dedicated core for real-time guest a symmetric multi-processor (SMP) system, preventing the real-time guest from being adversely affected by harmful workloads.  Approaches Process pinning System call: sched_setaffinity() Tools: taskset/cpuset Interrupt pinning File interface: /proc/irq/ /smp_affinity 14

BTLab Embedded Virtualization Group Outline  Introduction  Performance Analysis  PerformanceTuning Methods  Experimental Results  Conclusion 15

BTLab Embedded Virtualization Group Experimental Results (VxWorks)  Interrupt Response Time (IRT) 16

BTLab Embedded Virtualization Group Experimental Results (Linux)  Process Dispatch Latency Time (PDLT) 17

BTLab Embedded Virtualization Group Outline  Introduction  Performance Analysis  PerformanceTuning Methods  Experimental Results  Conclusion 18

BTLab Embedded Virtualization Group Conclusions  Virtualization software layer combined with various system loads do cause certain additional response latencies.  Real-time performance tunings methods under the host Linux can reduce the response latencies of the real-time guest to some degree.  With careful setup and tuning, sub-millisecond response time can be guaranteed on the KVM guest. 19

BTLab Embedded Virtualization Group Contributions  Propose an KVM-based embedded real-time virtualization architecture, which combines Linux and VxWorks together, as the guest GPOS and guest RTOS respectively.  Analyze how KVM combined other system loads introduces additional latencies to the guest interrupt response time  Evaluate the interrupt response time the KVM guest is able to achieve and the effectiveness of various performance tuning methods. 20

BTLab Embedded Virtualization Group End Thank you! Q&A 21

BTLab Embedded Virtualization Group Backup VMM VM scheduling VM

BTLab Embedded Virtualization Group Backup

BTLab Embedded Virtualization Group