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[Bug 1591487] Re: On funct remove_entity_load_avg issue.

 

................................
       │    │  mov    %eax,0x170(%rbx)                                                                          ▒
       │    │↑ jbe    db                                                                                        ▒
       │    │  shr    %edx                                                                                      ▒
       │    │  mov    $0xafb50401,%ecx                                                                          ▒
       │    │  shr    %r8                                                                                       ▒
       │    │  mov    %edx,%eax                                                                                 ▒
       │    │  mul    %ecx                                                                                      ▒
       │    │  movabs $0xafb504000afb5041,%rcx                                                                  ▒
       │    │  mov    %r8,%rax                                                                                  ▒
       │    │  shr    $0xe,%edx                                                                                 ▒
       │    │  mov    %edx,%r15d                                                                                ▒
       │    │  mul    %rcx                                                                                      ▒
       │    │  shr    $0xe,%rdx                                                                                 ▒
       │    │  cmp    $0x158,%rdi                                                                               ▒
       │    │  mov    %rdx,%r14                                                                                 ▒
       │    │↑ ja     109                                                                                       ▒
       │    │  mov    %rdx,0x8(%rsp)                                                                            ▒
       │    │  callq  0xffffffff810b2c10                                                                        ▒
       │    │  mov    0x8(%rsp),%rdx                                                                            ▒
       │    │↑ jmpq   109                                                                                       ▒
       │1f4:│  mov    %rdx,0x160(%rdi)                                                                          ▒
       │    │  mov    0x178(%rdi),%r14                                                                          ▒
       │    │↑ jmpq   127                                                                                       ▒
100,00 │207:│  movq   $0x0,0x168(%rbx)                                                                          ▒
       │    │  movl   $0x0,0x170(%rbx)                                                                          ▒
       │    │  xor    %r14d,%r14d                                                                               ▒
       │    │  xor    %edx,%edx

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https://bugs.launchpad.net/bugs/1591487

Title:
  On funct remove_entity_load_avg issue.

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  On function remove_entity_load_avg from file http://lxr.free-
  electrons.com/source/kernel/sched/fair.c#L2647

  http://lxr.free-electrons.com/source/kernel/sched/fair.c#L3000
  my processor spent 100 cycles to move nonexistent data on %rbx.
  On this funct exist embbeded function with issue  .

  Bellow isresult 
  $perf record -e cycles -ag and thern perf report.

  remove_entity_load_avg  /proc/kcore                                                                              
         │                                                                                                        ▒
         │                                                                                                        ▒
         │                                                                                                        ▒
         │     Disassembly of section load0:                                                                      ▒
         │                                                                                                        ▒
         │     ffffffff810bbcb0 <load0>:                                                                          ▒
         │       nop                                                                                              ▒
         │       push   %rbp                                                                                      ◆
         │       mov    %rsp,%rbp                                                                                 ▒
         │       push   %r15                                                                                      ▒
         │       push   %r14                                                                                      ▒
         │       push   %r13                                                                                      ▒
         │       push   %r12                                                                                      ▒
         │       push   %rbx                                                                                      ▒
         │       mov    %rdi,%rbx                                                                                 ▒
         │       and    $0xfffffffffffffff0,%rsp                                                                  ▒
         │       sub    $0x10,%rsp                                                                                ▒
         │       mov    0x150(%rdi),%r13                                                                          ▒
         │       mov    0x60(%r13),%rdx                                                                           ▒
         │       mov    %rdx,%rax                                                                                 ▒
         │       sub    0x160(%rdi),%rax                                                                          ▒
         │     ↓ js     1f4                                                                                       ▒
         │       shr    $0xa,%rax                                                                                 ▒
         │       test   %rax,%rax                                                                                 ▒
         │     ↓ je     120                                                                                       ▒
         │       mov    %rdx,0x160(%rdi)                                                                          ▒
         │       mov    0x174(%rdi),%edx                                                                          ▒
         │       mov    %rdx,%rcx                                                                                 ▒
         │       add    %rax,%rdx                                                                                 ▒
         │       cmp    $0x3ff,%rdx                                                                               ▒
         │     ↓ jbe    14d                                                                                       ▒
         │       mov    $0x400,%edx                                                                               ▒
         │       movl   $0x0,0x174(%rdi)                                                                          ▒
         │       sub    %ecx,%edx                                                                                 ▒
         │       sub    %rdx,%rax                                                                                 ▒
         │       mov    %rax,%rdi                                                                                 ▒
         │       and    $0x3ff,%eax                                                                               ▒
         │       shr    $0xa,%rdi                                                                                 ▒
  Press 'h' for help on key bindings

  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
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/pcmC0D0p:   asu        3213 F...m pulseaudio
   /dev/snd/controlC0:  asu        3213 F.... pulseaudio
  CurrentDesktop: MATE
  Date: Sat Jun 11 13:12:03 2016
  InstallationDate: Installed on 2016-04-29 (42 days ago)
  InstallationMedia: Ubuntu-Studio 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
  IwConfig:
   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
  RelatedPackageVersions:
   linux-restricted-modules-4.4.0-22-generic N/A
   linux-backports-modules-4.4.0-22-generic  N/A
   linux-firmware                            1.157
  RfKill:
   
  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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