Each CPU can have a different request into the PLL (phase locked loop),
but the highest one wins, and their vote does not count if they are in
an idle state deeper than C1. You can observe this manually by reading
the pstate request and granted MSRs directly (requires msr-tools, and
the msr module must already be loaded). Example (requested, granted,
100% load on CPU 3):

root@s15:/home/doug/temp-git-git# rdmsr --bitfield 15:8 -d -a 0x199
16
16
16
38
16
16
16
16
root@s15:/home/doug/temp-git-git# rdmsr --bitfield 15:8 -d -a 0x198
36
35
36
36
36
36
36
36

Where 38 is the max and 16 in the min for my i7-2600K.
Why only 36 granted? because actually I guess three cores are active at the 
time of the sample. From turbostat:

cpu0: MSR_TURBO_RATIO_LIMIT: 0x23242526
35 * 100.0 = 3500.0 MHz max turbo 4 active cores
36 * 100.0 = 3600.0 MHz max turbo 3 active cores
37 * 100.0 = 3700.0 MHz max turbo 2 active cores
38 * 100.0 = 3800.0 MHz max turbo 1 active cores

Note: I ran the above as root because there is a lot over overhead
running it under "sudo", which tends to result in another CPU requesting
a high pstate by the time the sample is actually taken.

Now, the different reported CPU frequencies, for your example where
there is no dominant load, is another story. While there is only one
PLL, your mostly idle CPUs would be "awake" at different times, with the
PLL ramping up and down based on which incoming votes and requests are
being used.

Hope this helps, and apologies for this digression on this bug report.

-- 
You received this bug notification because you are a member of Desktop
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https://bugs.launchpad.net/bugs/1768976

Title:
  Ubuntu 18.04 is overheating after upgrade from 16.04

Status in linux package in Ubuntu:
  Confirmed
Status in xserver-xorg-video-nouveau package in Ubuntu:
  Confirmed

Bug description:
  Ubuntu is overheating at my laptop. Opening youtube on firefox is
  enough for critical temperature shutdown.

  Using lm-sensors for monitoring on 18.04 the temp varies between 70 and 85°C 
with only firefox or chrome open and doing nothing. 
  On my old 16.04 with same using, the temp varies between 55 and 70°C.

  First thought was the driver nouveau is the problem, and finally I was
  able to install by add "nouveau.modeset=0" at livecd boot options,
  without temp shutdown.

  After install I disable the nouveau at modprobe blacklist, but the
  system continues overheating and shutdown with basic usage.

  
  I have no idea what's happening with the bionic at my laptop.

  My laptop is a Samsung RF411 i5 2nd Generation and Geforce 540M.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.17
  ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
  Uname: Linux 4.15.0-20-generic x86_64
  NonfreeKernelModules: wl
  ApportVersion: 2.20.9-0ubuntu7
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  Date: Thu May  3 16:22:40 2018
  InstallationDate: Installed on 2018-04-27 (6 days ago)
  InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  Symptom: dist-upgrade
  UpgradeStatus: No upgrade log present (probably fresh install)
  VarLogDistupgradeAptHistorylog:
   Start-Date: 2018-04-27  15:46:02
   End-Date: 2018-04-27  15:46:02
  VarLogDistupgradeAptlog:
   Log time: 2018-04-27 15:45:39.753331
   Starting pkgProblemResolver with broken count: 0
   Starting 2 pkgProblemResolver with broken count: 0
   Done
   Log time: 2018-04-27 15:46:04.859979
  VarLogDistupgradeApttermlog:
   Log started: 2018-04-27  15:46:02
   Log ended: 2018-04-27  15:46:02
  --- 
  .tmp.unity_support_test.0:
   
  ApportVersion: 2.20.9-0ubuntu7.1
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  edir       2354 F.... pulseaudio
  CompositorRunning: None
  DistUpgraded: Fresh install
  DistroCodename: bionic
  DistroRelease: Ubuntu 18.04
  DistroVariant: ubuntu
  DkmsStatus:
   bcmwl, 6.30.223.271+bdcom, 4.15.0-20-generic, x86_64: installed
   bcmwl, 6.30.223.271+bdcom, 4.15.0-22-generic, x86_64: installed
  GraphicsCard:
   Intel Corporation 2nd Generation Core Processor Family Integrated Graphics 
Controller [8086:0116] (rev 09) (prog-if 00 [VGA controller])
     Subsystem: Samsung Electronics Co Ltd 2nd Generation Core Processor Family 
Integrated Graphics Controller [144d:c0a5]
     Subsystem: Samsung Electronics Co Ltd GF108M [GeForce GT 540M] [144d:c0a5]
  HibernationDevice: RESUME=UUID=e7a61aee-64c2-4c88-b4e1-4de481d0f88d
  InstallationDate: Installed on 2018-04-27 (36 days ago)
  InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
  MachineType: SAMSUNG ELECTRONICS CO., LTD. RF511/RF411/RF711
  NonfreeKernelModules: wl
  Package: xserver-xorg-video-nouveau 1:1.0.15-2
  PackageArchitecture: amd64
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-22-generic 
root=UUID=db38a22c-0e9f-4e1a-b9f7-f7aac2544394 ro quiet splash nouveau.runpm=0
  ProcVersionSignature: Ubuntu 4.15.0-22.24-generic 4.15.17
  PulseList:
   Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not 
accessible: Permission denied
   No PulseAudio daemon running, or not running as session daemon.
  RelatedPackageVersions:
   linux-restricted-modules-4.15.0-22-generic N/A
   linux-backports-modules-4.15.0-22-generic  N/A
   linux-firmware                             1.173.1
  Tags:  bionic ubuntu
  Uname: Linux 4.15.0-22-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups:
   
  _MarkForUpload: True
  dmi.bios.date: 04/26/2011
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 10HX.M034.20110426.SSH
  dmi.board.asset.tag: To be filled by O.E.M.
  dmi.board.name: RF511/RF411/RF711
  dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
  dmi.board.version: 10HX
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 9
  dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
  dmi.chassis.version: N/A
  dmi.modalias: 
dmi:bvnAmericanMegatrendsInc.:bvr10HX.M034.20110426.SSH:bd04/26/2011:svnSAMSUNGELECTRONICSCO.,LTD.:pnRF511/RF411/RF711:pvr10HX:rvnSAMSUNGELECTRONICSCO.,LTD.:rnRF511/RF411/RF711:rvr10HX:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvrN/A:
  dmi.product.family: To be filled by O.E.M.
  dmi.product.name: RF511/RF411/RF711
  dmi.product.version: 10HX
  dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.
  version.compiz: compiz 1:0.9.13.1+18.04.20180302-0ubuntu1
  version.libdrm2: libdrm2 2.4.91-2
  version.libgl1-mesa-dri: libgl1-mesa-dri 18.0.0~rc5-1ubuntu1
  version.libgl1-mesa-glx: libgl1-mesa-glx 18.0.0~rc5-1ubuntu1
  version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4
  version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
  version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
  version.xserver-xorg-video-intel: xserver-xorg-video-intel 
2:2.99.917+git20171229-1
  version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2

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