Messages in this thread | | | From | "Doug Smythies" <> | Subject | RE: [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs_pct on governor switch | Date | Wed, 7 Oct 2015 15:26:00 -0700 |
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On 2015.10.07 15:06 Rafael J. Wysocki wrote: > 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. Agreed. It is pm-suspend doing it.
>> 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.
Agreed. This in pm-utils, and not limited to Ubuntu. We can ignore this issue if everyone wants, but I can envision bug reports.
> 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).
I have no idea either, but the stated theory seems sound.
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