Hardware Virtualization Slower Than Software?

Jim Buzbee writes "Those you keeping up with the latest virtualization techniques being offered by both Intel and AMD will be interested in a new white paper by VMWare that comes to the surprising conclusion that hardware-assisted x86 virtualization oftentimes fails to outperform software-assisted virtualization. My reading of the paper says that this counterintuitive result is often due to the fact that hardware-assisted virtualization relies on expensive traps to catch privileged instructions while software-assisted virtualization uses inexpensive software substitutions. One example given is compilation of a Linux kernel under a virtualized Linux OS. Native wall-clock time: 265 seconds. Software-assisted virtualization: 393 seconds. Hardware-assisted virtualization: 484 seconds. Ouch. It sounds to me like a hybrid approach may be the best answer to the virtualization problem. "

Comments

Re:Sponsored by VMWare.. what do you expect?

[Anonymous Coward]

See title... VMWare make software virtualisation products. Of course they're going to try and find that software methods are better.

Disclaimer: I work for VMware.

1. VMware already supports VT, but it's not enabled by default because for normal workloads it's slower. If VT really were faster, do you really think we'd be choosing to use a slower approach and making customers unhappy?
2. Even Intel admits the first generation of VT hardware wasn't so great and now claims that they were aiming for correctness instead of performance:
   • http://x86vmm.blogspot.com/2006/04/intel-quietly-b acking-away-from-vt.html (from Keith's weblog)
   • http://news.com.com/Intel+feeds+virtualizations+ne ed+for+speed/2100-1006_3-6048217.html