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[Bug 1591491] Re: On function __update_load_avg issue.


This issue appears to be an upstream bug.  Would it be possible for you
to open an upstream bug report[0]? That will allow the upstream
Developers to examine the issue, and may provide a quicker resolution to
the bug.

Please follow the instructions on the wiki page[0]. The first step is to
email the appropriate mailing list. If no response is received, then a
bug may be opened on bugzilla.kernel.org.

Once this bug is reported upstream, please add the tag: 'kernel-bug-

[0] https://wiki.ubuntu.com/Bugs/Upstream/kernel

** Changed in: linux (Ubuntu)
   Importance: Undecided => Medium

** Changed in: linux (Ubuntu)
       Status: Confirmed => Triaged

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  On function __update_load_avg issue.

Status in linux package in Ubuntu:

Bug description:
  On this bug need litle explications function embedded
  __compute_runnable_contrib have at beggining on "big" noop by 100
  cycles but why?

  Looking bellow on contrib is added value but is not used for twice. 
  2715                 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
  2716                 contrib = __compute_runnable_contrib(periods);
  2717                 contrib = cap_scale(contrib, scale_freq);
  2718                 if (weight) {

  Look here :

  And content of perf :

  __compute_runnable_contrib  /proc/kcore                                                                          
         │    Disassembly of section load0:
         │    ffffffff810b2c70 <load0>:
  100,00 │      nop
         │      cmp    $0x20,%rdi
         │    ↓ ja     13
         │      mov    -0x7e5e84c0(,%rdi,4),%eax
         │    ← retq
         │13:   cmp    $0x158,%rdi
         │    ↓ ja     27
         │      push   %rbp
         │      mov    %rsp,%rbp
         │      callq  0xffffffff810b2c10
         │      pop    %rbp
         │    ← retq
         │27:   mov    $0xba7e,%eax
         │    ← retq

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: linux-image-4.4.0-22-generic 4.4.0-22.40
  ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
  Uname: Linux 4.4.0-22-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.1
  Architecture: amd64
   /dev/snd/pcmC0D0p:   asu        3213 F...m pulseaudio
   /dev/snd/controlC0:  asu        3213 F.... pulseaudio
  CurrentDesktop: MATE
  Date: Sat Jun 11 14:17:27 2016
  InstallationDate: Installed on 2016-04-29 (42 days ago)
  InstallationMedia: Ubuntu-Studio 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
   lo        no wireless extensions.
   enp1s0    no wireless extensions.
  MachineType: Olidata S.p.A. ALABAMA
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-22-generic root=/dev/mapper/192--168--0--108--vg-root ro
   linux-restricted-modules-4.4.0-22-generic N/A
   linux-backports-modules-4.4.0-22-generic  N/A
   linux-firmware                            1.157
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 07/08/2008
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: S0101
  dmi.board.asset.tag: To Be Filled By O.E.M.
  dmi.board.name: To be filled by O.E.M.
  dmi.board.vendor: To be filled by O.E.M.
  dmi.board.version: To be filled by O.E.M.
  dmi.chassis.asset.tag: To Be Filled By O.E.M.
  dmi.chassis.type: 3
  dmi.chassis.vendor: To Be Filled By O.E.M.
  dmi.chassis.version: To Be Filled By O.E.M.
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrS0101:bd07/08/2008:svnOlidataS.p.A.:pnALABAMA:pvrToBeFilledByO.E.M.:rvnTobefilledbyO.E.M.:rnTobefilledbyO.E.M.:rvrTobefilledbyO.E.M.:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
  dmi.product.name: ALABAMA
  dmi.product.version: To Be Filled By O.E.M.
  dmi.sys.vendor: Olidata S.p.A.

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