On Fri, 2004-01-30 at 12:52, Anshul Gupta wrote:Hi All,
I have upgraded the kernel from 2.4.20-28.9 to 2.4.24 on a 4-processor machine and somehow only 2 processors are detected now. All 4 processors were detected in 2.4.20-28.9.
Does the machine really have four physical CPUs? AFAIK, all P4 Xeon CPUs
support hyperthreading, which makes each physical CPU look like two
seperate CPUs when enabled. This counfused the crap out of me before the
penny dropped when I got my hands on a couple of dual-Xeon servers (dual
2.8Ghz chips in one, dual 2.4s in the other), since while I knew each
machine only had two CPUs, /proc/cpuinfo and dmesg showed 4.
Earlier 2.4 kernels reported each virtual CPU seperately, which is why my dual machines looked like they had four CPUs. Later versions are hyperthreading-aware, and report only the number of physical CPUs. I'm not sure when that change was made, but it's possible that it was somewhere between your two kernel versions.
Cheers, Anshul