On Wednesday, October 07, 2015 05:31:25 PM Prarit Bhargava wrote: > > On 10/07/2015 02:52 PM, Doug Smythies wrote: > > On 2015.10.07 08:46 Prarit Bhargava wrote: > >> On 10/07/2015 11:40 AM, Doug Smythies wrote: > >>> > >>> Do we agree or disagree that the root issue seems to be (from your test)?: > >>> > >>> \# echo 100 > /sys/devices/system/cpu/intel_pstate/min_perf_pct > >>> > >>> [ 21.483436] store_min_perf_pct[453] min_sysfs_pct = 100 > >>> [ 21.489373] store_min_perf_pct[456] min_perf_pct = 100 > >>> [ 21.495203] store_min_perf_pct[459] min_perf_pct = 100 > >>> [ 21.501050] store_min_perf_pct[462] min_perf_pct = 100 > >> > >> Yep, and it appears to be done by default in Fedora & RHEL :/ ... the > >> issue is > >> still the same IMO that min_sysfs_pct & max_sysfs_pct are not cleared on a > >> governor switch. > > > > Clearing them will break some other things. For example, and as > > shown in my original reply, resume from suspend. > > > > Why? Because, at least on my computer, the governor is changed to > > "performance" during suspend, and the "powersave" governor is > > restored sometime during resume. The users wants the settings they had > > before the suspend. > > > > Looking at this in more detail after having tested on a Intel(R) Core(TM) > i7-2600 CPU @ 3.40GHz in Fedora and RHEL. > > I have a feeling that the switch you're seeing (poweersave->performance, > suspend > ... resume, performance->powersave) is occurring in userspace, and not as a > result of the kernel. IMO if userspace changes the governor, all bets are off > on maintaining max_sysfs_pct and min_sysfs_pct. > > Here's something I cannot figure out (because I do not have an Ubuntu > install). > *Why* is Ubuntu making the governor switch during suspend/resume? Is it > because of archaic brokeness they were trying to paper over?
That's not limited to Ubuntu, pm-utils has been doing that forever. I have no idea why has it been doing that, though. I guess the reason was to "speed up" PM transitions (in case it started when you were in a low-frequency P-state and then there was no time to bump it up before things got too far). Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
