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Message #94682
[Bug 1386473] Re: Not using all cores after upgrade to 14.10
I'm attaching the patch for the cherry-pick of the upstream fix. I tried
to do it in proper Ubuntu kernel format. :-)
Is there anything else you need to get this into Utopic?
** Patch added: "0001-sched-x86-Fix-up-typo-in-topology-detection.patch"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1386473/+attachment/4276798/+files/0001-sched-x86-Fix-up-typo-in-topology-detection.patch
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https://bugs.launchpad.net/bugs/1386473
Title:
Not using all cores after upgrade to 14.10
Status in linux package in Ubuntu:
Confirmed
Status in linux source package in Utopic:
Confirmed
Bug description:
I have a computer with two cpus with 4 cores each (physical) but htop
is only showing activity on two of these 8 cores (number 1 and 3).
Also, if I run "stress -c 8" top shows only 25% cpu usage. I've
rebooted the machine and the problem persists. I also took a look at
the BIOS settings and found nothing there that looked suspicious.
If I run 'stress -c 8' only two cores go to 100% in htop as stated
above (cores 1 and 3). If I run 'stress -c 1', one core goes to 100%
(either core 1 or 3). If I run taskset -cp <coreid> <pid> I can
control which core the process is run on. I can actually move it to
any core that I want (1, 3 or any other one)! So the cores are
there... the kernel just doesn't seem to use it unless I explicitly
tell it to with taskset.
I've verified that this is a regression when moving from [lxk]ubuntu
14.04 to 14.10. I used pristine lubuntu 14.10 and 14.04 usb sticks to
test this out and verified that a cpu sysbench test using 8 threads
took ~15 sec on 14.04 but ~55 sec on 14.10. The computer this is
happening on is a Dell Precision T5400 tower workstation.
ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: linux-image-3.16.0-23-generic 3.16.0-23.31
ProcVersionSignature: Ubuntu 3.16.0-23.31-generic 3.16.4
Uname: Linux 3.16.0-23-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CRDA: Error: [Errno 2] No such file or directory: 'iw'
CurrentDesktop: KDE
Date: Tue Oct 28 00:46:25 2014
HibernationDevice: RESUME=UUID=20536d9f-ef05-46dd-a104-47367e464fcd
InstallationDate: Installed on 2014-02-05 (264 days ago)
InstallationMedia: Ubuntu-Server 13.10 "Saucy Salamander" - Release amd64 (20131016)
IwConfig:
eth0 no wireless extensions.
lo no wireless extensions.
MachineType: Dell Inc. Precision WorkStation T5400
ProcFB:
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.16.0-23-generic root=UUID=28fc4c4c-cecd-4abe-a788-28f69e745845 ro splash quiet
RelatedPackageVersions:
linux-restricted-modules-3.16.0-23-generic N/A
linux-backports-modules-3.16.0-23-generic N/A
linux-firmware 1.138
RfKill:
SourcePackage: linux
UpgradeStatus: Upgraded to utopic on 2014-10-24 (3 days ago)
dmi.bios.date: 02/01/2008
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A01
dmi.board.name: 0RW203
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 7
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA01:bd02/01/2008:svnDellInc.:pnPrecisionWorkStationT5400:pvr:rvnDellInc.:rn0RW203:rvrA00:cvnDellInc.:ct7:cvr:
dmi.product.name: Precision WorkStation T5400
dmi.sys.vendor: Dell Inc.
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