On Tue, Jul 17, 2018 at 12:21 PM, Andreas Herrmann <aherrm...@suse.com> wrote: > On Tue, Jul 17, 2018 at 12:09:21PM +0200, Rafael J. Wysocki wrote: >> On Tuesday, July 17, 2018 11:36:20 AM CEST Andreas Herrmann wrote: >> > On Tue, Jul 17, 2018 at 11:27:21AM +0200, Andreas Herrmann wrote: >> > > On Tue, Jul 17, 2018 at 11:23:25AM +0200, Rafael J. Wysocki wrote: >> > > > On Tue, Jul 17, 2018 at 11:11 AM, Andreas Herrmann >> > > > <aherrm...@suse.com> wrote: >> > > > > On Tue, Jul 17, 2018 at 11:06:29AM +0200, Rafael J. Wysocki wrote: >> > > > >> On Tue, Jul 17, 2018 at 10:50 AM, Andreas Herrmann >> > > > >> <aherrm...@suse.com> wrote: >> > > > >> >> > > > >> [cut] >> > > > >> >> > > > >> > >> > > > >> > On balance before this commit users could use pcc-cpufreq but had >> > > > >> > already suboptimal performance (compared to say intel_pstate >> > > > >> > driver >> > > > >> > which can be used changing BIOS options). >> > > > >> >> > > > >> BTW, I wonder why you need to change the BIOS options for >> > > > >> intel_pstate to load. >> > > > > >> > > > > I think this is because of (in intel_pstate_init()): >> > > > > >> > > > > /* >> > > > > * The Intel pstate driver will be ignored if the platform >> > > > > * firmware has its own power management modes. >> > > > > */ >> > > > > if (intel_pstate_platform_pwr_mgmt_exists()) >> > > > > return -ENODEV; >> > > > > >> > > > >> > > > OK, because of the "Proliant" entry, right? >> > > > >> > > > So it looks like we have an issue there. We find the entry and we >> > > > look for _PSS. It is not there, so we assume that the firmware is >> > > > expected to control performance, which is not the case. >> > >> > FYI, there is another BIOS setting on those systems. It's called >> > "Collaborative Power Control" (AFAIK enabled by default). >> > >> > Only if this is disabled, firmware is (alone) in control of >> > performance. (And of course in this case neither pcc-cpufreq nor >> > intel_pstate will be loaded). >> >> OK, the patch is below. >> >> First, I hope that if "Collaborative Power Control" is disabled, it will >> simply hide the PCCH object and so intel_pstate will still not load then. > > PCCH is hidden in that case.
OK >> The main question basically is what the OS is expected to do if >> "Dynamic Power Savings Mode" is set. If we are *expected* to use >> the PCC interface then, intel_pstate may not work in that case, but >> I suspect that the PCC interface allows extra energy to be saved >> over what is possible without it. > > I'll test it and see what happens. Thanks!
