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Xenalyze: Finding meaning in the chaos
 

Xenalyze: Finding meaning in the chaos

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The Xen has a tracing infrastructure that can collect a large amount of very detailed data about what's happening at the hypervisor layer. But making sense out of that data isn't an easy thing to do. ...

The Xen has a tracing infrastructure that can collect a large amount of very detailed data about what's happening at the hypervisor layer. But making sense out of that data isn't an easy thing to do. In this talk I give an overview of xenalyze, a powerful tool I've developed for finding meaning in the vast amounts of data generated by xentrace, enabling both debugging and performance analysis.

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    Xenalyze: Finding meaning in the chaos Xenalyze: Finding meaning in the chaos Presentation Transcript

    • Xenalyze Finding meaning in the chaos George Dunlap [email_address] Citrix Systems, UK Ltd
    • Introduction
      • Modern operating systems are complex
      • Xentrace for gathering in-depth information
      • Too much information
      • Xenalyze
    • Talk goals
      • Those for whom xenalyze is useful will use it
      • Basic understanding of what xenalyze does, and what it’s useful for
    • Outline
      • Overview of Xen tracing
      • When xentrace is useful
      • Core functionality of xenalyze
      • Xenalyze as a platform
      • Case studies
    • Xen tracing
      • Trace records
        • Single 4-byte event number
        • Optional TSC timestamp
        • Optional trace-specific data, up to 28 bytes
      • Event mask to control which events are logged
      • Per-cpu trace buffers
      • Buffers read by process in dom0, copied to disk
    • Xen tracing: What it’s good for
      • Key attributes
        • Lots of detailed data
        • Moderate cpu, disk overhead
        • Not persistent on host crash
      • Understand both macro and micro effects
        • Performance analysis
        • Debugging
        • Understanding guest behavior
      • Comparing to other techniques
        • printk
        • Xenoprof
        • Xen performance counters
    • Key trace events
      • Runstate change
        • Figure out who’s running where
        • Analyze how much time is spent blocked, preempted, waiting after wake, &c
      • VMEXIT / VMENTER
        • How much time, and for what reason, we’re spending time in Xen
    • Xenalyze: Core functionality
      • Problem: xentrace file not in order
        • Attempt to process records in order
      • Mapping small to large
        • Aggregate information to see larger trends
      • Data is per-cpu, but we want per-vcpu
        • Track vcpus across physical cpus
    • Example output, dump mode Xen Summit AMD 2010
    • Example output, Summary mode Xen Summit AMD 2010
    • Example output, Interval Xen Summit AMD 2010
    • Example output, Scatterplot Xen Summit AMD 2010
    • Advanced features
      • “ Enumeration” of MMIO, IO, addresses, and so on
      • Symbol file translation
      • Linear pagetable back-calculation
      • Wake-to-halt, by interrupt
      • … and many more
    • Platform for new analysis
      • Xenalyze may not be able to answer the questions you have
      • But it’s a great platform to modify, because it’s already done a lot of the hard work for you
    • Case study: WinXP and TPR Xen Summit AMD 2010
    • Case study: WinXP and TPR, cont Xen Summit AMD 2010
    • Case study: Shadow Performance Xen Summit AMD 2010
    • Case study: Shadow perf, con’t Xen Summit AMD 2010 Out-of-sync Sync OS action Fix-up fault (TLB miss) Access Emulate Real PTE Emulate Transition PTE Propagate Propagate Page fault
    • Case study: Shadow perf, con’t Xen Summit AMD 2010 Out-of-sync Sync OS action Emulate Unmap PTE Fix-up fault (TLB miss) Access Emulate Map PTE
    • Outline
      • Overview of Xen tracing
      • When xentrace is useful
      • Core functionality of xenalyze
      • Xenalyze as a platform
      • Case studies
    • Talk goals
      • Those for whom xenalyze is useful will use it
      • Basic understanding of what xenalyze does, and what it’s useful for
    • Questions
      • Download now:
      • http://xenbits.xensource.com/ext/xenalyze