I am seeing the following suspicious behavior on one of our web servers (IIS 6.0 on win2k3). two CPUs hyperthreaded into 4.
In task manager and perfmon the w3wp.exe's cpu utilization does appear to be floored at 25%. By floored I mean, cpu utilization never goes below that number, and sticks at that value even when the server handles no requests. Furthermore looking at the performance tab in task manager, the utilization of the individual cpus fluctuates widely, but the overall cpu utilization stays constant at 25%. I.e. the widely varying values from the for cpus just happen to always add up to 25%.
To me there appears to be something wrong with these counters. It counts as if 1 cpu (of the 4) is completely utilized, when in fact it might not be.
Any idea what might be going on there? Anyone seen something similar before? (another machine in the same cluster exhibits similar behavior, just that it has w3wp.exe counted as consuming 50% of the cpu, again with virtually no traffic).