On 04.05.2023 19:00, Jason Andryuk wrote:
> On Thu, May 4, 2023 at 10:35 AM Jan Beulich <jbeul...@suse.com> wrote:
>>
>> On 01.05.2023 21:30, Jason Andryuk wrote:
>>> When using HWP, some of the returned data is not applicable. In that
>>> case, we should just omit it to avoid confusing the user. So switch to
>>> printing the base and turbo frequencies since those are relevant to HWP.
>>> Similarly, stop printing the CPU frequencies since those do not apply.
>>
>> It vaguely feels like I have asked this before: Can you point me at a
>> place in the SDM where it is said that CPUID 0x16's "Maximum Frequency"
>> is the turbo frequency? Without such a reference I feel a little uneasy
>> with ...
>
> I don't have a reference, but I found it empirically to match the
> "turbo" frequency.
>
> For an Intel® Core™ i7-10810U,
> https://ark.intel.com/content/www/us/en/ark/products/201888/intel-core-i710810u-processor-12m-cache-up-to-4-90-ghz.html
>
> Max Turbo Frequency 4.90 GHz
>
> # xenpm get-cpufreq-para
> cpu id : 0
> affected_cpus : 0
> cpuinfo frequency : base [1600000] turbo [4900000]
>
> Turbo has to be enabled to reach (close to) that frequency.
>
> From my cover letter:
> This is for a 10th gen 6-core 1600 MHz base 4900 MHZ max cpu. In the
> default balance mode, Turbo Boost doesn't exceed 4GHz. Tweaking the
> energy_perf preference with `xenpm set-cpufreq-hwp balance ene:64`,
> I've seen the CPU hit 4.7GHz before throttling down and bouncing around
> between 4.3 and 4.5 GHz. Curiously the other cores read ~4GHz when
> turbo boost takes affect. This was done after pinning all dom0 cores,
> and using taskset to pin to vCPU/pCPU 11 and running a bash tightloop.
Right, but what matters for the longer term future is what gets committed
(and the cover letter won't be). IOW ...
>>> @@ -720,10 +721,15 @@ static void print_cpufreq_para(int cpuid, struct
>>> xc_get_cpufreq_para *p_cpufreq)
>>> printf(" %d", p_cpufreq->affected_cpus[i]);
>>> printf("\n");
>>>
>>> - printf("cpuinfo frequency : max [%u] min [%u] cur [%u]\n",
>>> - p_cpufreq->cpuinfo_max_freq,
>>> - p_cpufreq->cpuinfo_min_freq,
>>> - p_cpufreq->cpuinfo_cur_freq);
>>> + if ( internal )
>>> + printf("cpuinfo frequency : base [%u] turbo [%u]\n",
>>> + p_cpufreq->cpuinfo_min_freq,
>>> + p_cpufreq->cpuinfo_max_freq);
>>
>> ... calling it "turbo" (and not "max") here.
>
> I'm fine with "max". I think I went with turbo since it's a value you
> cannot sustain but can only hit in short bursts.
... I don't mind you sticking to "turbo" as long as the description makes
clear why that was chosen despite the SDM not naming it this way.
Jan
