It was recently pointed out to me that the CPU driver is printing (a very poorly worded) message to the system error log every time it receives a _PPC change notification. For those who don't know what a _PPC is, it's an ACPI object that informs the OS which of the defined P-states are accessible. That is, it's like a governor on which P-states the OS should use. It's frequently used by the platform to force the processors down to a lower frequency as a thermal control mechanism.
The _PPC can change dynamically and when it does it is possible for the OS to find out about the change by registering a change notification handler. The CPU driver does register a handler and as I mentioned above is printing an error message to the system error log it is invoked. Printing the message to the system error log was apparently a mistake. Some platforms are changing the _PPC values much more often that I expected. I've already filed: 6636222 "NOTICE: cpudrv_pm_set_topspeed: instance 0: has new max power of 2000 MHz" needs to go to remove the message. But was thinking that we might want to add another cpu_info kstat to track the current maximum permissible frequency for the processor. It would have to be an x86 only kstat probably tracked in the cpu_t structure in a similar fashion as cpu_curr_clock. I was wondering if anyone had an opinion on the usefulness of this data as a cpu_info kstat addition? Mark
