After speaking to Dell's support they realized that I had to remove the option
acpi=off from my
/boot/grub/menu.1st config file. Apparently ACPI support is essential for hyper-threading, but is turned off by default when installing CentOS 6.2.
I have a Dell server with two Intel Xeon E5645 cpus, each cpu has 6 cores, and each core is hyperthreaded (i.e. should be equivalent to two virtual cores). I installed CentOS 6.2 on this server and it seems to detect only 12 cores (although there should be 24 virtual cores altogether).
When I look at
/proc/cpuinfo I get for each cpu:
cpu cores: 6 siblings: 6
Which seems to indicate that number of cores equals number of virtual cores, or hyperthreading not detected/enabled.
When I run
dmidecode I can see that HT flag is turned on and I do see the following, which seem to indicate that the BIOS is configured correctly for hyperthreading.
Core Count: 6 Core Enabled: 6 Thread Count: 12
Is there some configuration that I am missing in order to make Linux detect all virtual cores?