张俊 1080379124 [email protected] 2011.1 1. btlab embedded virtualization group outline ...

张俊 1080379124

[email protected]

2011.1

1

BTLab Embedded Virtualization Group

Outline Introduction Performance Analysis PerformanceTuning Methods Experimental Results Conclusion

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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 App

Hardware

Guest OS

App App

Guest OS

App App

Host(VMM)

Hardware

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Motivation

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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


System Consolidation Multi-core enablement for legacy embedded

uni-processor applications

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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

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Embedded Real-Time Architecture

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Multi-core CPU with virtualization extension KVM as the hypervisor Linux as the GPOS VxWorks as the RTOS



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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

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swctxschedulinglatencynellatencyISRIRT tttttPDLT ker


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

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PrioritizationA 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

ApproachesShell command: chrt System Call: sched_setscheduler()

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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.

ApproachesProcess pinning

System call: sched_setaffinity() Tools: taskset/cpuset

Interrupt pinning File interface: /proc/irq/<irq_number>/smp_affinity

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Experimental Results (VxWorks)Interrupt Response Time (IRT)

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Experimental Results (Linux)Process Dispatch Latency Time (PDLT)

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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.

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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.

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End

Thank you!Q&A

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Backup

VMM VM scheduling


Backup

张俊 1080379124 [email protected] 2011.1 1. btlab embedded virtualization group outline ...

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