[brendangregg]

The thermal throttle limit (PROCHOT), according to the MSRs, is 95. I did read through the various thermal status and thermal log MSRs, which were always zero, suggesting we aren't thermal throttling. Although I'm not sure those MSR bits are exposed by Xen. (They probably are, since the other bits in the same MSR are.)

Just checking the Intel manual docs:

"• Thermal Status (bit 0, RO) — This bit indicates whether the digital thermal sensor high-temperature output signal (PROCHOT#) is currently active. Bit 0 = 1 indicates the feature is active. This bit may not be written by software; it reflects the state of the digital thermal sensor.

• Thermal Status Log (bit 1, R/WC0) — This is a sticky bit that indicates the history of the thermal sensor high temperature output signal (PROCHOT#). Bit 1 = 1 if PROCHOT# has been asserted since a previous RESET or the last time software cleared the bit. Software may clear this bit by writing a zero."

I was checking both, and both were zero.

So if we aren't thermal throttling, then I guess it still may be the fans...