Request increase CONFG_NR_CPUS= higher than 8 for linux-generic-pae

[Christian Nygaard]

Binary package hint: linux-generic-pae

In linux-generic-pae 32-bit kernel the config parameter CONFIG_NR_CPUS=8 is set to 8 this is to little for modern multicore CPUs. Suggestion is that this parameter is set to either 32 or 64. CONFIG_NR_CPUS=64 is the value used in the 64-bit kernel.

Steps to reproduce:
$ grep CONFIG_NR_CPUS /boot/config-2.6.32-24-generic-pae

./linux-2.6.32/debian.master/config/i386/config.flavour.generic-pae

uname -a output:
Linux ubuntu 2.6.32-24-generic-pae #39-Ubuntu SMP Wed Jul 28 07:39:26 UTC 2010 i686 GNU/Linux

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: linux-generic-pae 2.6.32.24.25
Regression: No
Reproducible: Yes
ProcVersionSignature: Ubuntu 2.6.32-24.39-generic-pae 2.6.32.15+drm33.5
Uname: Linux 2.6.32-24-generic-pae i686
AlsaDevices: Error: command ['ls', '-l', '/dev/snd/'] failed with exit code 2: ls: cannot access /dev/snd/: No such file or directory
AplayDevices: aplay: device_list:223: no soundcards found...
Architecture: i386
ArecordDevices: arecord: device_list:223: no soundcards found...
Date: Tue Aug 24 13:25:34 2010
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100427.1)
MachineType: Supermicro X8DTU
PciMultimedia:

ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-24-generic-pae root=UUID=6676f6ff-18ff-47cd-baca-d6a638a1b800 ro quiet splash
ProcEnviron:
 PATH=(custom, no user)
 LANG=sv_SE.utf8
 SHELL=/bin/bash
SourcePackage: linux
UdevDb: Error: [Errno 2] Filen eller katalogen finns inte
dmi.bios.date: 05/28/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 2.0
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: X8DTU
dmi.board.vendor: Supermicro
dmi.board.version: 1234567890
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 17
dmi.chassis.vendor: Supermicro
dmi.chassis.version: 1234567890
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr2.0:bd05/28/2010:svnSupermicro:pnX8DTU:pvr1234567890:rvnSupermicro:rnX8DTU:rvr1234567890:cvnSupermicro:ct17:cvr1234567890:
dmi.product.name: X8DTU
dmi.product.version: 1234567890
dmi.sys.vendor: Supermicro

[penalvch (penalvch)]

Christian Nygaard, thank you for reporting this and helping make Ubuntu better. As of Trusty this would still be 8:
git clone git://kernel.ubuntu.com/ubuntu/ubuntu-trusty.git && grep -r CONFIG_NR_CPUS= | grep i386
debian.master/config/i386/config.common.i386:CONFIG_NR_CPUS=8

I'll mark this Triaged for now, so this request could be further reviewed.

As well, could you please provide a full detail on why you are making this request? Is this just a general "it would be nice..." or would you have a requirement in your environment for PAE, that migrating to amd64 would be too onerous?

Despite this, from the perspective of just one data point, if one is utilizing 8+ cores, then it may be best to switch to the amd64 version of the kernel for performance reasons -> http://www.phoronix.com/scan.php?page=article&item=ubuntu_x86_1304&num=1 .

[Po-Hsu Lin (cypressyew)]

Closing this bug with Won't fix as this kernel / release is no longer supported.
Please feel free to open a new bug report if you're still experiencing this on a newer release (Bionic 18.04.3 / Disco 19.04)
Thanks!