2016-04-01 18:46 GMT+02:00 Jörg Otte <jrg.o...@gmail.com>: > 2016-04-01 17:20 GMT+02:00 Doug Smythies <dsmyth...@telus.net>: >> On 2016.04.01 05:40 Rafael J. Wysocki wrote: >>> On Friday, April 01, 2016 11:20:42 AM Jörg Otte wrote: >>>> 2016-03-31 17:43 GMT+02:00 Rafael J. Wysocki <r...@rjwysocki.net>: >>>>> On Thursday, March 31, 2016 05:25:18 PM Jörg Otte wrote: >>>>>> 2016-03-31 13:42 GMT+02:00 Rafael J. Wysocki <r...@rjwysocki.net>: >>>>>>> On Thursday, March 31, 2016 11:05:56 AM Jörg Otte wrote: >> >>>> >>>> here they are. >>>> >> >>> First of all, the sampling mechanics works as expected >>> in the failing case, which is the most important thing >>> I wanted to know. >> >> Yes, but that might be part of the problem, as for some CPUs >> there is never a long duration, and thus the long duration >> check never kicks in driving the target pstate down. >> >>> The core_busy column is clearly suspicious and it >>> looks like CPUs 2 and 3 never really go idle. >> >> This has been observed several times before [1]. >> Due to beat frequencies between desktop type frame rates >> and such, the worst manifestation of the issue seems to be >> for 300 Hz kernels, but Ubuntu uses uses 250 Hz. >> >> Oh look, Jörg is using 300 Hz!! >> >> $ grep CONFIG_HZ .config_jorg >> # CONFIG_HZ_PERIODIC is not set >> # CONFIG_HZ_100 is not set >> # CONFIG_HZ_250 is not set >> CONFIG_HZ_300=y >> # CONFIG_HZ_1000 is not set >> CONFIG_HZ=300 >> > > I use 300Hz because of: > "250 Hz is a good compromise choice allowing server performance > while also showing good interactive responsiveness even > on SMP and NUMA systems. If you are going to be using NTSC video > or multimedia, selected 300Hz instead." (from KBuild helptext) > > -> I often use multimedia so according this text 300 Hz is the better > choice. > >>> I guess we'll need to find out >>> why they don't go idle to get to the bottom of this, but it firmly falls >>> into >>> the weird stuff territory already. > >> I'm compiling a 300 Hz kernel now, also with "# CONFIG_NO_HZ is not set", > > Again from KBuild helptext: > "CONFIG_NO_HZ: > This is the old config entry that enables dynticks idle. > We keep it around for a little while to enforce backward > compatibility with older config files." > > -> NO_HZ outdated. > >> but I have never been able to re-create these type of findings before. >> >> I have also tried several other things in an attempt re-create Jörg's >> Case, so far without success. >> >> References: >> [1] https://bugzilla.kernel.org/show_bug.cgi?id=93521 >> In particular: >> https://bugzilla.kernel.org/show_bug.cgi?id=93521#c35 >> https://bugzilla.kernel.org/show_bug.cgi?id=93521#c42 >> https://bugzilla.kernel.org/show_bug.cgi?id=93521#c77 >> >> ... Doug > > > Nevertheless, I'll try setting 250Hz + NO_HZ > For me no improvements. Neither 300->250Hz nor NO_HZ_IDLE + NO_HZ
Thanks, Jörg
