Hi! > On 2019.06.12 14:25 Rafael J. Wysocki wrote: > > On Wed, Jun 12, 2019 at 4:45 AM Doug Smythies <dsmythies@xxxxxxxxx> wrote: > >> > >> So, currently there seems to be 3 issues in this thread > >> (and I am guessing a little, without definitive data): > >> > >> 1.) On your system Kernel 5.4-rc2 (or 4) defaults to the intel_pstate CPU frequency > >> scaling driver and the powersave governor, but kernel 4.6 defaults to the > >> acpi-cpufreq CPU frequency scaling driver and the ondemand governor. > > > > Which means that intel_pstate works in the active mode by default and > > so it uses its internal governor. > > Note sure what you mean by "internal governor"? > If you meant HWP (Hardware P-state), Pavel's processor doesn't have it. > If you meant the active powersave governor code within the driver, then agreed. > > > That governor is more performance-oriented than ondemand and it very > > well may cause more power to be allocated for the processor - at the > > expense of the GPU. > > O.K. I mainly use servers and so have no experience with possible GPU > verses CPU tradeoffs. > > However, I did re-do my tests measuring energy instead of CPU frequency > and found very little difference between the acpi-cpufreq/ondemand verses > intel_pstate/powersave as a function of single threaded load. Actually, > I did the test twice, one at 20 hertz work/sleep frequency and also > at 67 hertz work/sleep frequency. (Of course, Pavel's processor might > well have a different curve, but it is a similar vintage to mine > i5-2520M verses i7-2600K.) The worst difference was approximately > 1.1 extra processor package watts (an extra 5.5%) in the 80% to 85% > single threaded load range at 67 hertz work/sleep frequency for > the intel-pstate/powersave driver/governor. > > What am I saying? For a fixed amount of work to do per work/sleep cycle > (i.e. maybe per video frame related type work) while the CPU frequency Verses load > curves might differ, the resulting processor energy curve differs much less. > (i.e. the extra power for higher CPU frequency is for less time because it gets > the job done faster.) So, myself, I don't yet understand why only the one method > would have hit thermal throttling, but not the other (if indeed it > doesn't). It seems there are serious differences in reporting :-(. How do I determine which frequency CPU really runs at, in 4.6 kernel? But it seems that your assumptions are incorrect for my workload. flightgear is single-threaded, and in my configuration saturates the CPU, because it would like to achieve higher framerate than my system is capable of. > Just for information: CPU frequency verses single threaded load curves > for the conservative governor is quite different between the two drivers. > (tests done in February, perhaps I should re-do and also look at energy > at the same time, or instead of CPU frequency.) So this might be my problem? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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