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Message #186630
[Bug 1597419] [NEW] On __fget_light function issue
Public bug reported:
Bellow is result of perf record:
__fget_light /proc/kcore
│ ↓ je 30
│ push %rbp
│ mov %rsp,%rbp
│ callq 0xffffffff8122a6a0
│ test %rax,%rax
│ ↓ je 54
0,83 │ or $0x1,%rax
│ pop %rbp
│ ← retq
│30: mov 0x20(%rax),%rax
1,65 │ cmp (%rax),%edi
0,83 │ ↓ jae 51
0,83 │ mov 0x8(%rax),%rax
0,83 │ mov %edi,%edi
│ lea (%rax,%rdi,8),%rax
2,48 │ mov (%rax),%rax
2,48 │ test %rax,%rax
│ ↓ je 51
│ test %esi,0x44(%rax)
70,25 │ ┌──jne 51
│ │ repz retq
│51:└─→xor %eax,%eax
│ ← retq
│54: xor %eax,%eax
│ pop %rbp
│ ← retq
and i attached one patch wich descrease from 70-100 cycles stall to 23 cycles stall on function.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-28-generic 4.4.0-28.47
ProcVersionSignature: Ubuntu 4.4.0-28.47-generic 4.4.13
Uname: Linux 4.4.0-28-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: asu 2742 F.... pulseaudio
CurrentDesktop: MATE
Date: Wed Jun 29 18:50:46 2016
InstallationDate: Installed on 2016-04-29 (61 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-4.4.0-28-generic root=/dev/mapper/192--168--0--108--vg-root ro
RelatedPackageVersions:
linux-restricted-modules-4.4.0-28-generic N/A
linux-backports-modules-4.4.0-28-generic N/A
linux-firmware 1.157.1
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.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Confirmed
** Tags: amd64 apport-bug xenial
** Patch added: "Tested on linux-4.6.2"
https://bugs.launchpad.net/bugs/1597419/+attachment/4692316/+files/decrease_stal_cyc.patch
--
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Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1597419
Title:
On __fget_light function issue
Status in linux package in Ubuntu:
Confirmed
Bug description:
Bellow is result of perf record:
__fget_light /proc/kcore
│ ↓ je 30
│ push %rbp
│ mov %rsp,%rbp
│ callq 0xffffffff8122a6a0
│ test %rax,%rax
│ ↓ je 54
0,83 │ or $0x1,%rax
│ pop %rbp
│ ← retq
│30: mov 0x20(%rax),%rax
1,65 │ cmp (%rax),%edi
0,83 │ ↓ jae 51
0,83 │ mov 0x8(%rax),%rax
0,83 │ mov %edi,%edi
│ lea (%rax,%rdi,8),%rax
2,48 │ mov (%rax),%rax
2,48 │ test %rax,%rax
│ ↓ je 51
│ test %esi,0x44(%rax)
70,25 │ ┌──jne 51
│ │ repz retq
│51:└─→xor %eax,%eax
│ ← retq
│54: xor %eax,%eax
│ pop %rbp
│ ← retq
and i attached one patch wich descrease from 70-100 cycles stall to 23 cycles stall on function.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-28-generic 4.4.0-28.47
ProcVersionSignature: Ubuntu 4.4.0-28.47-generic 4.4.13
Uname: Linux 4.4.0-28-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: asu 2742 F.... pulseaudio
CurrentDesktop: MATE
Date: Wed Jun 29 18:50:46 2016
InstallationDate: Installed on 2016-04-29 (61 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-4.4.0-28-generic root=/dev/mapper/192--168--0--108--vg-root ro
RelatedPackageVersions:
linux-restricted-modules-4.4.0-28-generic N/A
linux-backports-modules-4.4.0-28-generic N/A
linux-firmware 1.157.1
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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