On 2016.03.30 08:52 Jörg Otte wrote: > 2016-03-30 17:33 GMT+02:00 Pandruvada, Srinivas > <srinivas.pandruv...@intel.com>: >> On Wed, 2016-03-30 at 13:05 +0200, Rafael J. Wysocki wrote: >>> On Wed, Mar 30, 2016 at 12:17 PM, Jörg Otte <jrg.o...@gmail.com>
>>>>>> Now in v4.6-rc1 the characteristic has dramatically changed. >>>>>> If in idle the processor frequency is more or less a few >>>>>> MHz around 2500Mhz. >>>>>> I currently use acpi_cpufreq which works as usual. >>>>>> Processor: Intel(R) Core(TM) i5-4200M CPU @ 2.50GHz >>>>>> (family: 0x6, model: 0x3c, stepping: 0x3) >> I want to reproduce this if I can. Can you give us info about your >> setup (Linux distribution, laptop model etc.)? I would like to try to reproduce the issue also. > Distro: Ubuntu 14.04.4 LTS Note that with Ubuntu 14.04, I had issues where my CPU would lock at pstate 24 (not always 24, but usually), regardless of load. However, it was always after an S3 suspend, occurred 100% of the time, and was independent of intel_pstate or acpi-cpufreq CPU frequency scaling drivers. Since changing my test server to Ubuntu server edition 16.04 (development version), I have not had those issues. While I have no proof, I have assumed the issue elimination was somehow related to the change to systemd. It might be worth observing both what the intel_pstate is asking for and what the processor is actually doing. What is being asked for: # rdmsr --bitfield 15:8 -d -a 0x199 What is being given: # rdmsr --bitfield 15:8 -d -a 0x198 An old problematic example from an idle system (mine) Note, my minimum pstate is 16: What was being given: # rdmsr --bitfield 15:8 -d -a 0x198 24 24 24 24 24 24 24 24 What was being asked for: # rdmsr --bitfield 15:8 -d -a 0x199 16 16 16 16 16 16 16 16 To gain further insight, it might also be worth acquiring some trace data. On an otherwise idle system, do: # perf record -a --event=power:pstate_sample sleep 300 If pressed for time, your sleep time can be less than 5 minutes, but try to get at least 100 seconds. The resulting perf.data file will be too big to include as an on-list attachment, but send it (or them) to me off-list for post processing, and I'll report back. ... Doug
