On 10/14/2015 08:29 PM, Rafael J. Wysocki wrote: > On Wednesday, October 14, 2015 07:59:38 PM Prarit Bhargava wrote: >> >> On 10/14/2015 05:09 PM, Kristen Carlson Accardi wrote: >>> On Wed, 14 Oct 2015 07:41:59 -0400 >>> Prarit Bhargava <[email protected]> wrote: >>> >>>> On systems that initialize the intel_pstate driver with the performance >>>> governor, and then switch to the powersave governor will not transition to >>>> lower cpu frequencies until >>>> /sys/devices/system/cpu/intel_pstate/min_perf_pct >>>> is set to a low value. >>>> >>>> The behavior of governor switching changed after commit a04759924e25 >>>> ("[cpufreq] intel_pstate: honor user space min_perf_pct override on >>>> resume"). The commit introduced tracking of performance percentage >>>> changes via sysfs in order to restore userspace changes during >>>> suspend/resume. The problem occurs because the global values of the newly >>>> introduced max_sysfs_pct and min_sysfs_pct are not lowered on the governor >>>> change and this causes the powersave governor to inherit the performance >>>> governor's settings. >>>> >>>> A simple change would have been to reset max_sysfs_pct to 100 and >>>> min_sysfs_pct to 0 on a governor change, which fixes the problem with >>>> governor switching. However, since we cannot break userspace[1] the fix >>>> is now to give each governor its own limits storage area so that governor >>>> specific changes are tracked. >>>> >>>> I successfully tested this by booting with both the performance governor >>>> and the powersave governor by default, and switching between the two >>>> governors (while monitoring /sys/devices/system/cpu/intel_pstate/ values, >>>> and looking at the output of cpupower frequency-info). Suspend/Resume >>>> testing was performed by Doug Smythies. >>>> >>>> [1] Systems which suspend/resume using the unmaintained pm-utils package >>>> will always transition to the performance governor before the suspend and >>>> after the resume. This means a system using the powersave governor will >>>> go from powersave to performance, then suspend/resume, performance to >>>> powersave. The simple change during governor changes would have been >>>> overwritten when the governor changed before and after the suspend/resume. >>>> I have submitted https://bugzilla.redhat.com/show_bug.cgi?id=1271225 >>>> against Fedora to remove the 94cpufreq file that causes the problem. It >>>> should be noted that pm-utils is obsoleted with newer versions of systemd. >>>> >>>> Cc: Kristen Carlson Accardi <[email protected]> >>>> Cc: "Rafael J. Wysocki" <[email protected]> >>>> Cc: Viresh Kumar <[email protected]> >>>> Cc: [email protected] >>>> Cc: Doug Smythies <[email protected]> >>>> Signed-off-by: Prarit Bhargava <[email protected]> >>> >>> Acked-by: Kristen Carlson Accardi <[email protected]> >>> >>> BTW - I think I can see an issue here with HWP enabled systems. It >>> looks to me like the hwp settings will not be programmed correctly >>> during a governor switch. This probably needs to be addressed in a >>> separate patch. >>> >> >> Oh, I see it now too. I'll get to that in another patch. Thanks for >> pointing >> that out Kristen. > > The $subject patch doesn't apply any more after the series from Srinivas that > I've just applied. > > Can you please rebase it on top of my bleeding-edge branch? >
Sure -- can you send me a pointer to the branch? P. > Thanks, > Rafael > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
