topic Re: No of physical processors on RedHat in Operating System - Linux

No of physical processors on RedHat

Alpa Shah — Mon, 02 Apr 2007 07:33:50 GMT

I want to get the no of physical processors on RedHat. Here is the o/p of cat /proc/cpuinfo.
Can any one tell me the no of CPUs this system has? Is the CPU count really 4 ? or its showing 4 because of dual core processors?

slx86sus10t3:/ # cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 15
model : 33
model name : Dual Core AMD Opteron(tm) Processor 270
stepping : 2
cpu MHz : 1991.427
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow pni lahf_lm cmp_legacy ts fid vid ttp
bogomips : 3988.18

processor : 1
vendor_id : AuthenticAMD
cpu family : 15
model : 33
model name : Dual Core AMD Opteron(tm) Processor 270
stepping : 2
cpu MHz : 1991.427
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow pni lahf_lm cmp_legacy ts fid vid ttp
bogomips : 3982.90

processor : 2
vendor_id : AuthenticAMD
cpu family : 15
model : 33
model name : Dual Core AMD Opteron(tm) Processor 270
stepping : 2
cpu MHz : 1991.427
cache size : 1024 KB
physical id : 1
siblings : 2
core id : 0
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow pni lahf_lm cmp_legacy ts fid vid ttp
bogomips : 3982.87

processor : 3
vendor_id : AuthenticAMD
cpu family : 15
model : 33
model name : Dual Core AMD Opteron(tm) Processor 270
stepping : 2
cpu MHz : 1991.427
cache size : 1024 KB
physical id : 1
siblings : 2
core id : 1
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow pni lahf_lm cmp_legacy ts fid vid ttp
bogomips : 3982.81

Re: No of physical processors on RedHat

Ivan Ferreira — Mon, 02 Apr 2007 09:28:42 GMT

You should have two physical processors because the physical id is the same for two of the cpu listed. You have physical id 0 for cpu0 and cpu1, and physical id 1 for cpu2 and cpu3.

Re: No of physical processors on RedHat

Jerome Forissier — Mon, 02 Apr 2007 11:03:40 GMT

This is a 2-CPU system, each CPU being dual-core. So, strictly speaking, the number of physical processors is 2. However, since you have 4 cores, you may have 4 processes (or threads) running simultaneously.

Re: No of physical processors on RedHat

Alpa Shah — Mon, 02 Apr 2007 23:42:39 GMT

Thanks a lot to both of you. I got ur point.

Re: No of physical processors on RedHat

Alpa Shah — Mon, 02 Apr 2007 23:56:34 GMT

One more doubt,
I've an RH4 m/c which shows 2 processors with same physical id with command `cat /proc/cpuinfo`. And these processors are not dual core. Then why is it showing 2 processors? Is it because the processor may support hyperthreading technology. I am not sure if it is supporting Hyperthreading. Is there any way I can check?

Re: No of physical processors on RedHat

Stuart Browne — Tue, 03 Apr 2007 00:22:21 GMT

Dual core and Hyperthreading both show up in this manner.

Re: No of physical processors on RedHat

Jerome Forissier — Tue, 03 Apr 2007 02:30:41 GMT

Hyper-Threading is the 'ht' flag. However multi-core CPUs also show this flag...
So, I think that:
- if you see the 'ht' flag but 'cpu cores' is 1, then you have a 'regular' Hyper-Threaded CPU;
- if you see the 'ht' flag and 'cpu cores' is >1, then you have a multi-core CPU.