Fewer than expected CPUs are online

General questions.
Post Reply
eugene
Posts: 6
Joined: December 13th, 2018, 6:21 am

Fewer than expected CPUs are online

Post by eugene » January 7th, 2019, 6:53 am

Hi folks,

I'm running ipfire on an Intel Xeon Silver 4114. The server CPU specs are:
- 2 sockets
- 10 core/CPU
- 2 threads/core

dmidecode shows the correct CPU count but lscpu shows that only 32 are online. Printing "processor" from /proc/cpuinfo further confirms the fact.

Code: Select all

$ dmidecode -t processor | grep "Thread Count"
	Thread Count: 20
	Thread Count: 20

$ lscpu | grep "^CPU(s).*"
CPU(s):                32

$ cat /proc/cpuinfo |grep processor
processor	: 0
processor	: 1
processor	: 2
processor	: 3
processor	: 4
processor	: 5
processor	: 6
processor	: 7
processor	: 8
processor	: 9
processor	: 10
processor	: 11
processor	: 12
processor	: 13
processor	: 14
processor	: 15
processor	: 16
processor	: 17
processor	: 18
processor	: 19
processor	: 20
processor	: 21
processor	: 22
processor	: 23
processor	: 24
processor	: 25
processor	: 26
processor	: 27
processor	: 28
processor	: 29
processor	: 30
processor	: 31
This is the first time I've observed this discrepancy. Any ideas?

Thanks in advance!

eugene
Posts: 6
Joined: December 13th, 2018, 6:21 am

Re: Fewer than expected CPUs are online

Post by eugene » January 7th, 2019, 7:50 am

The max CPU count is pegged to 32 in the code. Anyone knows why this is so?

Code: Select all

$ grep NR_CPUS /boot/config-`uname -r`
CONFIG_NR_CPUS=32

User avatar
Deepcuts
Posts: 452
Joined: March 1st, 2016, 3:18 pm
Location: Romania

Re: Fewer than expected CPUs are online

Post by Deepcuts » January 7th, 2019, 11:39 am

The reason might be to keep the kernel size as low as possible.
I recall any extra CPU would increase the kernel by 8K.
In the past, many distros had even more drastic limitations, like 8-10 CPUs.
Image
Image

eugene
Posts: 6
Joined: December 13th, 2018, 6:21 am

Re: Fewer than expected CPUs are online

Post by eugene » January 7th, 2019, 1:38 pm

That's interesting. Is it necessary with today's hardware?

User avatar
MichaelTremer
Core Developer
Core Developer
Posts: 5681
Joined: August 11th, 2005, 9:02 am

Re: Fewer than expected CPUs are online

Post by MichaelTremer » January 7th, 2019, 1:43 pm

Hello,

indeed nobody has used a system with that man processor cores. You can file a ticket and I can assign that to Arne to increase this number in the next kernel release.

-Michael
Support the project with our Donation Challenge!

Get Commercial Support for IPFire and more from Lightning Wire Labs!

Image

eugene
Posts: 6
Joined: December 13th, 2018, 6:21 am

Re: Fewer than expected CPUs are online

Post by eugene » January 7th, 2019, 1:55 pm

Sure, but it so happens that my server has that many cores :D

Where should I file the ticket?

User avatar
MichaelTremer
Core Developer
Core Developer
Posts: 5681
Joined: August 11th, 2005, 9:02 am

Re: Fewer than expected CPUs are online

Post by MichaelTremer » January 7th, 2019, 2:02 pm

Support the project with our Donation Challenge!

Get Commercial Support for IPFire and more from Lightning Wire Labs!

Image

eugene
Posts: 6
Joined: December 13th, 2018, 6:21 am

Re: Fewer than expected CPUs are online

Post by eugene » January 8th, 2019, 2:37 am

Submitted it here https://bugzilla.ipfire.org/show_bug.cgi?id=11963.

Thanks heaps!

User avatar
MichaelTremer
Core Developer
Core Developer
Posts: 5681
Joined: August 11th, 2005, 9:02 am

Re: Fewer than expected CPUs are online

Post by MichaelTremer » January 8th, 2019, 11:56 am

eugene wrote:
January 8th, 2019, 2:37 am
Submitted it here https://bugzilla.ipfire.org/show_bug.cgi?id=11963.

Thanks heaps!
Thank you. A new kernel will be released with Core Update 128 which will include this change...
Support the project with our Donation Challenge!

Get Commercial Support for IPFire and more from Lightning Wire Labs!

Image

Post Reply