Enable hyperthreading 11.31 from OS
Tue, 01/27/2009 - 12:59 — liquid
HP uses the concept of logical CPUs (or LCPUs). On the Montecito processors, each CPU thread is one LCPU - thus EFI is reporting correctly: there are 2 CPUs, each with 2 cores and each core with 2 threads: 2 cores * 2 threads = 4 LCPUs per physical CPU (not core).
The kernel tunable lcpu_attr will activate use of hyperthreading by the OS; this will cause Glance to report on eight cores instead of four (as the "missing cores" will now show up as being in use).
The command is immediate and is:
kctune lcpu_attr=1