https://linux-kvm.org/api.php?action=feedcontributions&feedformat=atom&user=IroKVM - User contributions [en]2026-04-06T05:07:20ZUser contributionsMediaWiki 1.39.5https://linux-kvm.org/index.php?title=Guest_PMU&diff=4074Guest PMU2011-09-28T08:56:15Z<p>Iro: Fix presentation link</p>
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<div>Guest PMU (Performance Monitoring Unit) currently exists in the form of an out-of-tree patchset.<br />
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See the [http://www.linux-kvm.org/wiki/images/6/6d/Kvm-forum-2011-performance-monitoring.pdf KVM Forum 2011 presentation] about the state as of August 2011.<br />
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= Current status =<br />
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Version 1 Architectural PMU on Intel and AMD hosts is implemented and works.<br />
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= TODO =<br />
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== Guest visible features ==<br />
* Implement Version 2 Architectural PMU - allows faster switch times using PERF_GLOBAL_ENABLE MSR<br />
* Implement Version 3 Architectural PMU<br />
* Model specific PMU - allows access to more events and support for more tools; but restricts live migration capabilities<br />
** Need per-event validation to avoid leaking socket-wide or core-wide information<br />
* PEBS - Preceise Event Based Sampling - allows examining program state<br />
* BTS - Branch Trace Store - allows tracing program execution accurately<br />
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== Accuracy ==<br />
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* Update Joerg Roedel's exclude_guest/exclude_host patchset to support Intel hosts, using vmx's ability to load PERF_GLOBAL_ENABLE on vmentry/vmexit<br />
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== Performance ==<br />
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* Investigate reports that enabling the guest PMU reduces performance<br />
* Update the perf_event subsystem to make use of the PERF_GLOBAL_ENABLE MSR to speed up context switching, on both guest and host<br />
* Check whether perf_event does unnecessary RMW operations on MSRs, which are significantly slow in a guest<br />
* Add a paravirt batch MSR read/write facility, update perf to use it when available<br />
* Change perf to use an ordinary interrupt instead of NMI when profiling only user space, or only a guest (reduces work in NMI context)<br />
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= Git repositories =<br />
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Guest PMU: git://github.com/avikivity/kvm.git pmu<br />
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exclude_host: git://github.com/avikivity/kvm.git perf-guest-counting</div>Iro