missing number of cores in according to /proc/cpuinfo

centguy · 01-05-2010, 08:04 PM

Only lately I notice that my CentOS 5.2 does not detect a second core according to the /proc/cpuinfo :

Quote:

processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 Duo CPU T7500 @ 2.20GHz
stepping : 11
cpu MHz : 1200.000
cache size : 4096 KB
physical id : 0
siblings : 1
core id : 0
cpu cores : 1
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc up ida pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4426.68
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management:

When I boot to Fedora 9, I get :

Quote:

processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 Duo CPU T7500 @ 2.20GHz
stepping : 11
cpu MHz : 800.000
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm ida
bogomips : 4388.96
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management:

processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 Duo CPU T7500 @ 2.20GHz
stepping : 11
cpu MHz : 800.000
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
apicid : 1
initial apicid : 1
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm ida
bogomips : 4388.78
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management:

Who is at fault ? CentOS or the intel cpu ?

kbp · 01-05-2010, 09:55 PM

Are you running a non-smp kernel for CentOS ? ( uname -a )

centguy · 01-05-2010, 10:58 PM

here it is:

Quote:

centos52-64-fuj ~]$ uname -a
Linux centos52-64-fuj 2.6.18-92.el5 #1 SMP Tue Jun 10 18:51:06 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux

AlucardZero · 01-06-2010, 08:52 AM

Are you booting CentOS with the "maxcpus=1" kernel parameter?

Does /sys/devices/system/cpu/cpu1/online exist? Does it contain the numeral "0"? If so, echo "1" to that path.

Elv13 · 01-06-2010, 10:23 AM

add

Code:

cpu=2 cpus=2 maxcpu=2

in the grub command line when you boot and see if it work, you can add them dynamically by pressing escape, then "e" on the kernel line. To boot, press "enter" and "b"

centguy · 01-06-2010, 07:52 PM

added cpu=2 cpus=2 maxcpu=2 maxcpus=2

but still one core is detected.

Is it maxcpu or maxcpus ? Linux is more stringent than an English Literature professor at Cambridge.

AlucardZero · 01-07-2010, 08:19 AM

What's your entire boot line?

Does /sys/devices/system/cpu/cpu1/online exist? Does it contain the numeral "0"? If so, echo "1" to that path.

What does

Code:

grep SMP /boot/config-`uname -r`

return when booted into CentOS?

centguy · 01-07-2010, 11:21 PM

Quote:

[root@centos52-64-fuj cpu]# pwd
/sys/devices/system/cpu
[root@centos52-64-fuj cpu]# ls
cpu0 sched_mc_power_savings
[root@centos52-64-fuj cpu]#

boot line:

Quote:

title [2] CentOS (2.6.18-92.el5) @ sda4
root (hd0,3)
kernel /boot/vmlinuz-2.6.18-92.el5 ro root=LABEL=/12 rhgb quiet noapic cpu=2 cpus=2 maxcpu=2
initrd /boot/initrd-2.6.18-92.el5.img

Finally:

Quote:

[root@centos52-64-fuj grub]# uname -a
Linux centos52-64-fuj 2.6.18-92.el5 #1 SMP Tue Jun 10 18:51:06 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux

Quote:

[root@centos52-64-fuj grub]# grep SMP /boot/config-`uname -r`
# CONFIG_X86_VSMP is not set
CONFIG_SMP=y
CONFIG_SUSPEND_SMP=y

evo2 · 01-08-2010, 02:49 AM

I have a 4 CPU machine, and with some kernels, on some boots, only 3 CPUs are reported. I never worked out what the problem was, since it stopped happening a few years ago. So, what happens if you reboot?

Cheers,

Evo2.

centguy · 01-08-2010, 09:53 AM

I reboot it everyday, it is my laptop.

Elv13 · 01-08-2010, 02:40 PM

Quote:

Originally Posted by evo2

I have a 4 CPU machine, and with some kernels, on some boots, only 3 CPUs are reported. I never worked out what the problem was, since it stopped happening a few years ago. So, what happens if you reboot?

Cheers,

Evo2.

32bit kernel have support for many CPUs, but many distributions enabled the support only in "bigsmp" or "bigcpu" kernel because having support for 256 (now 1024) cpus added some complexity and weight in the running kernel. Now the "normal" max number is 4, but to have more you still have to enable them in kernel configs. That's why Linux don't see all core/cpu when a brand new generation arrive with 2x more cores. It happened again with the i7 (it showed only 4 out of 8, even with HT enabled).

is-1-prime? · 01-09-2010, 06:56 PM

I think the main reason is RHEL/CentOS kernels cannot handle certain features in the
Fujitsu LifeBook A6030 BIOS. Well, at least I know what combination of distro and machine I should carefully choose next time.

syg00 · 01-09-2010, 07:23 PM

Quote:

kernel /boot/vmlinuz-2.6.18-92.el5 ro root=LABEL=/12 rhgb quiet noapic cpu=2 cpus=2 maxcpu=2

That noapic is probably the problem - should be messages in dmesg to tell you you now only have 1 CPU active. Take it out, and all the cpu keywords you added.

centguy · 01-10-2010, 12:16 AM

If I take out noapic, there is tonnes of bothering system messages such as

Disabling IRQ #169

on all terminals. I believe one of my posts in LQ is about this.

I might give a boot without noapic and report back.

Thanks!

(p.s. The irq 169 problem has been "fixed" in my LQ thread:

http://www.linuxquestions.org/questi...irq-169-654086 )

centguy · 01-10-2010, 09:22 PM

Quote:

kernel /boot/vmlinuz-2.6.18-92.el5 ro root=LABEL=/12 rhgb quiet

is giving me two cores.

So the culprit is noapic. I have done some updates on the OS
along the way, it
seems the annoying irq messages disappear (let hope so, if not, I am going to use only one core to avoid annoying messages)