Comment 37 for bug 601986

I've been poking at this machine quite a bit over the past few weeks. I'll lay out what I know about this issue, which isn't a complete explanation.

There are various command-line parameters that seem to 'fix' this issue along with the overall performance problems seen with this machine. What all these workarounds ultimately seem to be doing is keeping the CPU busy enough that it seldom or never gets into idle states deeper than C1. You can force this behavior without affecting any other features (tickless, etc.) by passing intel_idle.max_cstate=1 on the kernel command-line. I've yet to see the disk driver or performance issues running with this option.

This points to a problem with deep C-states, which in turn points to an issue somewhere outside of the kernel. Other machines based on this chipset don't exhibit these problems, and loading newer microcode to the CPU doesn't help, so the most likely explanation is that the problem lies with the BIOS. This is something only Toshiba will be able to fix, so all we're left with are the various workarounds.

We're already planning to add some text to the natty release notes recommending to add "highres=off nohz=off" to the kernel command line in response to another BIOS-related issue (see bug 640100), which also effectively works around the issues here. Unfortunately that's probably the best we'll be able to do.