The Cause Of The Xen Linux Performance Issues
Written by Michael Larabel in Virtualization on 1 December 2011 at 10:10 AM EST. 2 Comments
Recently I published some controversial benchmark results of the Xen performance on the Linux 3.0 kernel compared to bare-metal and KVM virtualization along with noting awkward Linux power management when using Xen. The results were valid and have now been confirmed by Xen developers and they have narrowed down the cause of the serious performance issues.

The Xen Dom0 support in the mainline Linux 3.0 kernel lacks proper CPU power management support to be able to switch between the processor's different frequency states, which can leave Xen in an under-performing configuration in not being able to tap any of the Turbo Boost states while also burning through more power when the system is idle.

These patches still aren't upstream in the mainline Linux kernel, but hopefully they will make it for the Linux 3.3 kernel as right now the "out of the box" experience is rather poor.

Besides tracking down this ACPI power management issue in Xen, the developer investigating the issue also carried out some new performance benchmarks under Xen compared to bare-metal and against KVM virtualization. The findings can be found on the Xen blog. The Xen developers used the Phoronix Test Suite for carrying out the performance tests.
About The Author
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Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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