[lug] cpuinfo shows hyperthreading enabled, but no hyperthreading seen

Michael Hirsch mdhirsch at gmail.com
Fri Oct 12 13:45:17 MDT 2012


I have server with a single quad-core cpu.  It's a kinda old Xeon, and we'd
like to get the most out of it.  I had thought that it was a dual-core with
hyperthreading, but a bit more research shows that it is a quad-core with
no hyperthreading.

As you can see from this output, there are 4 processors and 4 cores, all on
one physical id.  I think this means that there are no CPUs due to
hyperthreading.  If you look at the flags, it has "ht" that I thought meant
hyperthreading is enabled, both in the BIOS and in the kernel.  But
apparently not.

Anyone know how to enable hyperthreading?

[root at manzanita log]# grep -E "processor|physical id|core id|flags"
/proc/cpuinfo
processor       : 0
physical id     : 0
core id         : 0
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
rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx smx est tm2
ssse3 cx16 xtpr sse4_1 sse4_2 popcnt lahf_lm
processor       : 1
physical id     : 0
core id         : 1
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
rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx smx est tm2
ssse3 cx16 xtpr sse4_1 sse4_2 popcnt lahf_lm
processor       : 2
physical id     : 0
core id         : 2
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
rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx smx est tm2
ssse3 cx16 xtpr sse4_1 sse4_2 popcnt lahf_lm
processor       : 3
physical id     : 0
core id         : 3
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
rdtscp lm constant_tsc ida nonstop_tsc pni monitor ds_cpl vmx smx est tm2
ssse3 cx16 xtpr sse4_1 sse4_2 popcnt lahf_lm

Thanks,

Michael
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