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#1 2024-02-18 16:24:32

alphalpha
Member
From: Germany
Registered: 2018-01-23
Posts: 139  

2 CPU threads went offline and wont come back

Hey All,

not shure what i did this time...
i just noticed in htop, that 2 of my 4 CPU threads are offline

lscpu | grep 'CPU(s)' -m3

CPU(s):                             4
On-line CPU(s) list:                0,1
Off-line CPU(s) list:               2,3

i tried chcpu as su -

chcpu -e 2
chcpu: CPU 2 enable failed: Operation not permitted

if i boot a live cd, all CPUs are working and chcpu also works

i tried an older kernel but that was not the problem

EDIT: i already tried restarting the pc cool
EDIT 2: 🎵

Last edited by alphalpha (2024-02-18 16:37:34)

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#2 2024-02-18 16:50:29

chris2be8
Member
Registered: 2018-08-11
Posts: 265  

Re: 2 CPU threads went offline and wont come back

What sort of CPU do you have? Is it 4 real cores or 2 cores with hypertheads?

Just post full output from lscpu if you are not sure of the answers.

And what make is the system? Can you see any clues in the BIOS?

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#3 2024-02-18 16:52:08

alphalpha
Member
From: Germany
Registered: 2018-01-23
Posts: 139  

Re: 2 CPU threads went offline and wont come back

2 cores with 2 threads

lscpu
Architecture:            x86_64
  CPU op-mode(s):        32-bit, 64-bit
  Address sizes:         36 bits physical, 48 bits virtual
  Byte Order:            Little Endian
CPU(s):                  4
  On-line CPU(s) list:   0,1
  Off-line CPU(s) list:  2,3
Vendor ID:               GenuineIntel
  Model name:            Intel(R) Core(TM) i7-3520M CPU @ 2.90GHz
    CPU family:          6
    Model:               58
    Thread(s) per core:  1
    Core(s) per socket:  2
    Socket(s):           1
    Stepping:            9
    CPU(s) scaling MHz:  37%
    CPU max MHz:         3600.0000
    CPU min MHz:         0.0000
    BogoMIPS:            5787.10
    Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflus
                         h dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc ar
                         ch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni p
                         clmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_
                         1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm cp
                         uid_fault epb pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid f
                         sgsbase smep erms xsaveopt dtherm ida arat pln pts md_clear flush_l1d
Virtualization features:
  Virtualization:        VT-x
Caches (sum of all):
  L1d:                   64 KiB (2 instances)
  L1i:                   64 KiB (2 instances)
  L2:                    512 KiB (2 instances)
  L3:                    4 MiB (1 instance)
NUMA:
  NUMA node(s):          1
  NUMA node0 CPU(s):     0,1
Vulnerabilities:
  Gather data sampling:  Not affected
  Itlb multihit:         KVM: Mitigation: VMX disabled
  L1tf:                  Mitigation; PTE Inversion; VMX conditional cache flushes, SMT disabled
  Mds:                   Mitigation; Clear CPU buffers; SMT disabled
  Meltdown:              Mitigation; PTI
  Mmio stale data:       Unknown: No mitigations
  Retbleed:              Not affected
  Spec rstack overflow:  Not affected
  Spec store bypass:     Mitigation; Speculative Store Bypass disabled via prctl
  Spectre v1:            Mitigation; usercopy/swapgs barriers and __user pointer sanitization
  Spectre v2:            Mitigation; Retpolines, IBPB conditional, IBRS_FW, RSB filling, PBRSB-eIBRS No
                         t affected
  Srbds:                 Vulnerable: No microcode
  Tsx async abort:       Not affected

it has nothing to do with the BIOS, since it works with a live cd

Last edited by alphalpha (2024-02-18 16:54:22)

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#4 2024-02-18 17:23:46

Altoid
Member
Registered: 2017-05-07
Posts: 1,429  

Re: 2 CPU threads went offline and wont come back

Hello:

alphaalpha wrote:

... since it works with a live cd.

At fist glance, it would seem (to me) that your local config is doing something (?) that the live cd is not doing.
Hence the difference in behaviour.

See here.

Use the chcpu command or the online sysfs attribute of a logical CPU to set a CPU online or offline.

Before you begin
   - Daemon processes like cpuplugd can change the state of any CPU at any time.     Such changes can interfere with manual changes.

You may want to consider following the procedure outlined in the linked page and see what gives.

That said, consider that cpu0 will always be on-line.
Check this and see what you get:

~$ cat /sys/devices/system/cpu/cpu1/online # <- 0 means off-line | 1 means on-line 
~$ cat /sys/devices/system/cpu/cpu2/online
~$ cat /sys/devices/system/cpu/cpu3/online

HTH.

Best,

A.

Last edited by Altoid (2024-02-18 17:34:17)

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#5 2024-02-18 17:32:34

alphalpha
Member
From: Germany
Registered: 2018-01-23
Posts: 139  

Re: 2 CPU threads went offline and wont come back

chcpu -r
chcpu: This system does not support rescanning of CPUs

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#6 2024-02-18 17:37:05

Altoid
Member
Registered: 2017-05-07
Posts: 1,429  

Re: 2 CPU threads went offline and wont come back

Hello:

... system does not support rescanning of CPUs

Hmm ...
Yes, that is what I get with my Intel Quad Q9550.

But what do you get when you do chcpu -r with the live CD?

and ...

What does uname -a get you with your local configuration and then with the live cd?

Best,

A.

Last edited by Altoid (2024-02-18 17:39:40)

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#7 2024-02-18 18:01:22

alphalpha
Member
From: Germany
Registered: 2018-01-23
Posts: 139  

Re: 2 CPU threads went offline and wont come back

with the live cd, chcpu -r still does not work, but -e 2 and -d 2 are working

local uname -a

Linux x 6.1.0-17-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.69-1 (2023-12-30) x86_64 GNU/Linux

live uname -a

Linux forge 6.1.0-13-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.55-1 (2023-09-29) x86_64 GNU/Linux

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#8 2024-02-18 20:13:47

Altoid
Member
Registered: 2017-05-07
Posts: 1,429  

Re: 2 CPU threads went offline and wont come back

Hello:

alphalpha wrote:

with the live cd, chcpu -r still does not work

Makes sense ...

chcpu -r
chcpu: This system does not support rescanning of CPUs

... it appears to be a system limitation.

But this ...

chcpu -e 2
chcpu: CPU 2 enable failed: Operation not permitted

... is a "no you cannot do that" reply.

The question is why the difference between live cd and local.

Please post your local and live cd system's printout for this:

~$ cat /proc/cmdline

and this:

~$ cat /sys/devices/system/cpu/cpu1/online 
~$ cat /sys/devices/system/cpu/cpu2/online
~$ cat /sys/devices/system/cpu/cpu3/online

Best,

A.

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#9 2024-02-20 14:09:45

alphalpha
Member
From: Germany
Registered: 2018-01-23
Posts: 139  

Re: 2 CPU threads went offline and wont come back

thx Altoid
whatever the cause was,
a fresh install will fix it, no big deal for me 😹

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#10 2024-02-20 14:18:22

Altoid
Member
Registered: 2017-05-07
Posts: 1,429  

Re: 2 CPU threads went offline and wont come back

Hello:

alphalpha wrote:

thx ...

You're welcome.

alphalpha wrote:

... no big deal for me ...

I see ...
Good to know.

Best,

A.

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