CPUs online or offline: Difference between revisions

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(Created page with " == Check CPU status == <syntaxhighlight lang="bash"> # get the list of offline CPUs cat /sys/devices/system/cpu/offline cat /sys/devices/system/cpu/online # get the list of online CPUs # get the list of CPUs ls -ld /sys/devices/system/cpu/cpu* # print individual CPU's online/offline status cat /sys/devices/system/cpu/cpu*/online # set online CPU <number> echo 1 > /sys/devices/system/cpu/cpu<number>/online or sudo chcpu -e <number> # set offline CPU <number> e...")
 
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This thread<ref>https://community.amd.com/t5/server-gurus-discussions/dual-socket-epyc-7702-64-cores-shows-254-cpu-online-1-cpu/m-p/350409</ref> shows system IOMMU enable in [[BIOS]] would be required to enable the last CPU core on Gigabyte system. However, it would be also related to other systems' BIOS configuration.
This thread<ref>https://community.amd.com/t5/server-gurus-discussions/dual-socket-epyc-7702-64-cores-shows-254-cpu-online-1-cpu/m-p/350409</ref> shows system IOMMU enable in [[BIOS]] would be required to enable the last CPU core on Gigabyte system. However, it would be also related to other systems' BIOS configuration.


smpboot: native_cpu_up is also related to [[x2APIC]]<ref>https://courses.cs.washington.edu/courses/cse451/24wi/documentation/x2apic.pdf</ref> features cause operating systems cannot use [[x2APIC]] unless Processor [[x2APIC]] [[Support]] is set to "Force Enabled" prior to booting.
smpboot: native_cpu_up is also related to [[x2APIC]]<ref>https://courses.cs.washington.edu/courses/cse451/24wi/documentation/x2apic.pdf</ref> features cause operating systems cannot use [[x2APIC]] unless Processor [[x2APIC]] [[Support]] is set to "Force Enabled" prior to booting OS.
 
 
x2APIC is depending on the BIOS configuration and type/version of OS,
 
* '''Windows Server 2016'''
** Windows Server 2016 supports AMD EPYC 7''xx''2-series CPUs, but this O.S. is limited to no more than 255 logical processors. Windows Server 2016 does not support X2APIC mode, and you should disable this mode in BIOS.
** '''AMD CBS-> CPU Common Options-> Performance-> CCD/Core/Thread Enablement ->Accept-> SMT control->Disabled (For ASUS BIOS)'''
 


== References ==
== References ==
<references />
<references />

Revision as of 13:42, 3 March 2024

Check CPU status

# get the list of offline CPUs
cat /sys/devices/system/cpu/offline

cat /sys/devices/system/cpu/online  
# get the list of online CPUs

# get the list of CPUs
ls -ld /sys/devices/system/cpu/cpu* 

# print individual CPU's online/offline status
cat /sys/devices/system/cpu/cpu*/online 

# set online CPU <number>
echo 1 > /sys/devices/system/cpu/cpu<number>/online 
or 
sudo chcpu -e <number>

# set offline CPU <number>
echo 0 > /sys/devices/system/cpu/cpu<number>/online
or 
sudo chcpu -d <number>

smpboot: native_cpu_up: bad cpu 255

This thread[1] shows system IOMMU enable in BIOS would be required to enable the last CPU core on Gigabyte system. However, it would be also related to other systems' BIOS configuration.

smpboot: native_cpu_up is also related to x2APIC[2] features cause operating systems cannot use x2APIC unless Processor x2APIC Support is set to "Force Enabled" prior to booting OS.


x2APIC is depending on the BIOS configuration and type/version of OS,

  • Windows Server 2016
    • Windows Server 2016 supports AMD EPYC 7xx2-series CPUs, but this O.S. is limited to no more than 255 logical processors. Windows Server 2016 does not support X2APIC mode, and you should disable this mode in BIOS.
    • AMD CBS-> CPU Common Options-> Performance-> CCD/Core/Thread Enablement ->Accept-> SMT control->Disabled (For ASUS BIOS)


References