Messages in this thread | | | Date | Mon, 8 Nov 2021 17:20:24 +0800 | From | Huang Rui <> | Subject | Re: [PATCH v3 00/21] cpufreq: introduce a new AMD CPU frequency control mechanism |
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On Sat, Nov 06, 2021 at 04:58:35PM +0800, Matt McDonald wrote: > > > I've tested this driver and it seems the results are a little > > > underwhelming. > > > The test machine is a two sockets server with two AMD EPYC 7713, > > > family:model:stepping 25:1:1, 128 cores/256 threads, 256G of memory > > > and SSD > > > storage. On this system, the amd-pstate driver works only in > > > "shared memory support", not in "full MSR support", > > > meaning that frequency switches are triggered from a workqueue > > > instead of scheduler context (!fast_switch). > > Huang, I've also done some detailed testing, and while many synthetic > benchmarks seem to show minimal differences between this new frequency > control mechanism and acpi_cpufreq, the general user experience seems a > bit degraded, but most of all, gaming performance in many instances (if > not all) is cut in half. Fully half. > > I have an RTX 3090 and a Ryzen 9 5900X, with 32GB (4x8) DDR4 3600. In
May we know the family/model id of your processors?
> Control with DLSS and RT enabled, on 5.15.rc5 with acpi_cpufreq, I get > 120-130 fps at 1440p. The same exact kernel with v3 of AMD_CPPC gives > me 50 fps. GPU usage is still at 100, but the CPU frequency is being > reported as like 5100Mhz*, and other assorted weirdness, but most > importantly the fps is stuck at 50. This is regardless of performance > scheduler (schedutil, ondemand, userspace or performance).
May we know your SMU version in your SBIOS?
Thanks, Ray
> > *My CPU can indeed boost over 5GHz on a single core here and there, but > this was constant and on all cores, so clearly it wasn't accurate. > > Also, from the documentation it looks like there's supposed to be a way > to fall back to acpi_cpufreq, but I found no such way to do that. If > AMD_CPPC was built into the kernel, I had to use amd-pstate, there was > no other option. Maybe I misinterpreted and acpi-cpufreq is only able > to be used as a fallback for CPUs that don't support amd-pstate. > > I know that gaming on Linux hasn't historically been one of AMD's > priorities with their CPUs, but with the Steam Deck upcoming I would > imagine this is a pretty important use-case, and I've tested multiple > games and they all lose a full 50% performance. I'm happy to test any > revisions or even kernel parameters or whatever else to try and get > this sorted. > > > > > Would you mind that we add a module param or filter the known good > > processors (mobile parts) to load amd-pstate. And others can use the > > param > > to switch between amd-pstate and acpi-cpufreq manually? After we > > address the > > performance gap, then we can switch it back. > > > This would be something I would be interested to try. > > > > > It seems the issue mainly from the processors with big number of > > cores and > > threads. Let's find the similiar family threadripper or EYPC > > processors to > > duplicate the test results. Will contact at you for details. :-) > > This may be an interesting route of investigation, I could potentially > try running a game with `taskset -c 0-7` or something similar. > > > >
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