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Date: Fri, 27 Nov 2015 14:01:39 +0800 From: Yu Chen <yu.c.chen@...el.com> To: Doug Smythies <dsmythies@...us.net> CC: "'Wysocki, Rafael J'" <rafael.j.wysocki@...el.com>, tglx@...utronix.de, hpa@...or.com, bp@...en8.de, "'Zhang, Rui'" <rui.zhang@...el.com>, linux-pm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org, "'Brown, Len'" <len.brown@...el.com>, 'Ingo Molnar' <mingo@...nel.org>, 'Pavel Machek' <pavel@....cz>, "'Pandruvada, Srinivas'" <srinivas.pandruvada@...el.com> Subject: Re: [PATCH] [v4] x86, suspend: Save/restore extra MSR registers for suspend Hi, On 11/27/2015 11:28 AM, Doug Smythies wrote: > On 2015.11.21 08:45 Doug Smythies wrote: >> On 2015.11.12 01:42 Chen, Yu C wrote: >>> On 2015.11.06 11:34 Doug Smythies wrote: > > [cut] > >>> rdmsr_safe might be better, > >> I'll look into it, thanks. > >>> you can refer to acpi_throttling_rdmsr > >> I don't understand. > >>> and I'm OK with this code, are you planning to send a formal patch? > >> The delay here is because I have always thought that some actual load >> content needs to be brought back to the intel_pstate driver, which would >> (or at least should) eliminate the need for this patch. > >> Anyway, and at least for the interim, I'll try to make and submit a formal version. > > I made a mistake in my initial testing. I put a 100% load on CPU 7 and then > cycled through all the clock modulation values to show that my test version of > a possible patch compensated / normalized the Clock Modulation. Indeed, if the > system is already asking for the maximum pstate, it will stay there. However, > whenever the load drops, the target pstate will drop to minimum and it will > never kick back up again, regardless of load. > Do you mean even with your patch applied, the cpufreq policy would choose a smaller target? I looked up the SDM, it says in 14.7.3: on Hyper-Threading Technology enabled processors, the clock modulation might behave differently: "if the programmed duty cycle is not identical for all logical processors in the same core, the processor core will modulate at the lowest programmed duty cycle " I dont know if this is related to the problem. > I am returning to my initial assertion copied below: > >>>>>>>> The current version of the intel_pstate driver is incompatible >>>>>>>> with any use of Clock Modulation, always resulting in driving the >>>>>>>> target pstate to the minimum, regardless of load. The result is >>>>>>>> the apparent CPU frequency stuck at minimum * modulation percent. >>>>>>> >>>>>>>> The acpi-cpufreq driver works fine with Clock Modulation, >>>>>>>> resulting in desired frequency * modulation percent. > > Chen, > > Thanks though for the suggestion to try normalizing. > I'll try to reproduce your problem, and let's discuss this offline. > ... Doug > thanks, Yu -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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