On Fri, Nov 20, 2020 at 09:26:08AM +0100, Otto Moerbeek wrote: > Hi, > > I got a new Ryzen machine, dmesg below. What I'm observing might be a > issue with hw.setperf. > > On startsup it shows: > > hw.cpuspeed=3800 > hw.setperf=100 > > If I lower hw.setperf to zero, the new state is reflect immediately in > hw.cpuspeed: > > hw.cpuspeed=2200 > hw.setperf=0 > > And also sha256 -t becomes slower as expected. > > But If I raise hw.setperf to 100 I'm seeing: > > hw.cpuspeed=2200 > hw.setperf=100 > > and sha256 -t is still slow. Only after some time passes (lets say a > couple of tens of seconds) it does show: > > hw.cpuspeed=3800 > hw.setperf=100 > > and sha256 -t is fast again. > > This behaviour is different from my old machine, where setting > hs.setperf was reflected in hs.cpuspeed immediately both ways > > Any clue? > > -Otto
Hey Otto, Nice machine! :-) I've seen this "sticking" issue before (as have others), but haven't been able to narrow it down unfortunately. I'm not sure if it's a bug in the k1x-pstate.c code I wrote, it's some undocumented new behaviour on newer Ryzen CPUs, or if a MI setperf change happened at some point that's unhandled.. At least on a desktop I'd suggest to leaved apmd(8) and not do any manual hw.setperf tweaking, you should have adequate cooling and the BIOS will automatically adjust the CPU fan to keep it so. I believe it will also allow it to more quickly move into CPB boost frequencies if left at P-state L0 (but don't quote me on that). -Bryan.
