On Fri, 13 Feb 2004, Lars Hecking wrote:
>> I have a dual-cpu box here (Dell PowerEdge 1750, 2x2.8GHz Xeon), but the OS
> reports 4 cpus. Why's that?
Your CPUs support HyperThreading (look at /proc/cpuinfo - your CPUs
will have the ht flag set), a feature of nearly all P4s that turns
your single CPU into 2 CPUs (albeit ones that share their caches). An
attempt by Intel to try offset the very long pipeline of P4 and high
cost of pipeline stalls/flushes.
For single-task, cache intensive workloads (eg computational), HT
costs performance. For most other workloads, HT is a win.
> Kernel: 2.4.20-28.9smp
>> $ dmesg | egrep -i '^CPU[0-9]|smp'
> CPU0: Intel(R) Xeon(TM) CPU 2.80GHz stepping 09
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