For the last few weeks, I've been working on adding support for KVM clock in the projects/paravirt branch. Currently, a KVM VM guest will end up selecting either the HPET or ACPI as the timecounter source. Unfortunately, this is very costly since every timecounter fetch causes a VM exit. KVM clock allows the guest to use the TSC instead; it is very similar to the existing Xen timer. The performance difference between HPET/ACPI and KVMCLOCK can be dramatic: a simple disk benchmark goes from 10K IOPs to 100K IOPs. The patch is attached is attached or available at [1]. I'd appreciate any testing. Also as a part of this, I've tried to generalized a bit of our existing hypervisor guest code, with the eventual goal of being able to support more invasive PV operations. The patch series is viewable in Phabricator. https://reviews.freebsd.org/D1429 - paravirt: Generalize parts of the XEN timer code into pvclock https://reviews.freebsd.org/D1430 - paravirt: Add interface to calculate the TSC frequency from pvclock https://reviews.freebsd.org/D1431 - paravirt: Add simple hypervisor registration and detection interface https://reviews.freebsd.org/D1432 - paravirt: Add detection of bhyve using new hypervisor interface https://reviews.freebsd.org/D1433 - paravirt: Add detection of VMware using new hypervisor interface https://reviews.freebsd.org/D1434 - paravirt: Add detection of KVM using new hypervisor interface https://reviews.freebsd.org/D1435 - paravirt: Add KVM clock timecounter support My current plan is to MFC this series to 10-STABLE, and commit a self-contained KVM clock to the other stable branches. [1] - https://people.freebsd.org/~bryanv/patches/kvm_clock-1.patch
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