As hyperthreading is disable the OS recognizes only two cpu (so I hope two physical cpu) but the problem is when I look to the cpu id (from cat /proc/cpuinfo), the two cpu physical id are identical !!!!!!!!!!!!!
and that 's should be only the case when the two cpu are not two physisal but two logical ...so my question is : is it a redhat bug or really a problem with cpu detection and use
Thanks for help
The processors have an instruction named CPUID. This returns the manufacture name, model number and feature set (extended instruction set). The instruction does not return a CPU serial number. Therefore on dual processor (or more). You typicaly will find all processors return same CPUID.
Imagine the trouble you would have if the system had two processors, one supporting SSE3 instructions and one that does not. If the O/S switches processors for an application after the application determined that SSE3 instructions were available then the program will fail. SMP usaly requires all processors support the same instruction set.
What code are you using to determine the cpu physical id number?
You might want to look at Detecting Support for Hyper-Threading Technology Enabled Processors on how to identify different physical (and logical) processors.
I am running a linux smp kernel 188.8.131.52 on a dual Xeon cpu server
hyper threading is disabled in the bios. To get the cpuid, I simply cat the /proc/cpuinfo and as a result, I see that there is two activated cpu but the cpu physical ID are identical for the two cpu (ID is 0 for both)
I looks very strange to me because usually when two physical cpu are activated and hyperthreading is disabled as the two cpu are physical the cpu ID are different (I work in a laboratory with different kind of intel architecture and I have already checked that cpu physical ID are different for different physical cpu)
As a result, my first feeling is : as the two cpu as the same id, my linux operating system only activates one cpu but I have no way at this time to confirm my feeling
What I did also is to enabled on this computer the HT in that case when I cat the /proc/cpuinfo I can see 4 processor (normal situation) with two logical cpu with the ID 0 and the two last cpu with the physical ID 6
So I do not understand why when HT is swiched off, the two cpu physical ID are not 0 and 6 and are in fact 0 and 0?
Do you know a way to checked effeciently my feeling? is it a linux operating system trouble or a hardware trouble (the server is a HP proliant DL 140 equipped with two Intel Xeon processors)