On 24.07.2019 17:35, Roger Pau Monné wrote: > On Wed, Jul 24, 2019 at 02:47:19PM +0000, Jan Beulich wrote: >> On 24.07.2019 16:36, Roger Pau Monné wrote: >>> On Wed, Jul 24, 2019 at 10:01:40AM -0400, Fredy P. wrote: >>>> My objective is to get CPU frequency throttling based on the >>>> temperature in a Xen/OpenWRT(dom0) system. >>>> >>>> After to expend hours reading Xen's wiki, mailing list archives, >>>> commits, googling and asking in the IRC channel I'm coming here asking >>>> for help because I hope there is something I miss and you could point >>>> it. >>> >>> That seems like an interesting project, I guess your focus is some >>> kind of low-power device? (not that it matters much for the context of >>> the question). >>> >>> Anyway, thanks for your interest on Xen and ways to improve it! >>> >>>> My first question is, there is any way to do CPU frequency throttling >>>> based on the temperature? >>> >>> I don't think there's such governor ATM implemented in Xen, the more >>> that I think all frequency throttling is supposed to be done by dom0 >>> using xenpm, but not Xen itself? >> >> The original authors of P- and C-state handling look to have >> assumed that T-state handling should work similarly, i.e. by >> Dom0 uploading relevant data. See public/platform.h starting at >> >> #define XENPF_set_processor_pminfo 54 >> >> where in particular you'll find >> >> #define XEN_PM_TX 2 > > OK, I assumed the question was about reading the CPU temperature and > then changing the frequency of the CPU, but not related to T-states.
Well, except that iirc T-states are (were) a means to control this via some governor, rather than "manually". Obtaining the CPU temperature should work (perhaps with some tweaks) the same way under Xen or on bare hardware. I also don't think hwmon devices get unintentionally "unexposed" when running under Xen. Their drivers may be written in ways that make them not work properly when run under Xen, though. > FWIW, there's an Intel article about T-states from 2013: > > https://software.intel.com/en-us/blogs/2013/10/15/c-states-p-states-where-the-heck-are-those-t-states > > That claims T-states are basically dead, and no modern processors > support them. Interesting; I wasn't aware of this. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
