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I just upgraded my bi-Xeon server with 20 cores/proc (i.e. a 40 cores server) from 18.04 to 20.04 and now the system is only viewing 1 processor!

The BIOS is correctly seeing the whole system (2 procs, 20 cores each)

The boot options are

Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.4.0-84-generic root=UUID=051241f1-7c3d-472a-b519-003008a805d4 ro mem_sleep_default=deep quiet splash acpi=off vt.handoff=7

Scrolling through dmesg output I find the following lines:

[    3.164688] smp: Bringing up secondary CPUs ...
[    3.164689] smp: Brought up 1 node, 1 CPU
[    3.164690] smpboot: Max logical packages: 1
[    3.164691] smpboot: Total of 1 processors activated (4200.00 BogoMIPS)

Please help...

ubfan1
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efji
  • 21

1 Answers1

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As ubfan1 suggested, the boot option "acpi=off" was the reason of the non-detection of the multiple processors. Without it, they are back! But the reason why I had added it was the control of the sleep mode: I wanted to avoid the server to enter in sleep mode after a few minutes of inactivity. It has been finaly achieved, without the "acpi=off" boot option, by modifying /etc/gdm3/greeter.dconf-defaults as suggested in the thread Ubuntu 20.04 server suspends or goes to sleep after a certain period of time, causing ssh to time out

efji
  • 21