Background: I have a whole mess of systems running the 2.6.20 and 2.6.22 kernel in what started as a Fedora Core 2 install several years ago. These systems have 8 cpus, as reported by cat /proc/cpuinfo.
My question is, when a process is running that uses multi-threading, does 99.99% CPU usage as reported by top mean 99.99% of every CPU or 99.99% total if you add the usage on each CPU together? In other words, should the maximum percentage be 800% or 100%?
It seems that when one of these processes is at 99.99%, if you look at each cpu individually, they will say 25% utilization (instead of 100%).
Any help is appreciated. If I was unclear or confusing, let me know and I will try to clarify.
UPDATE It seems as though we may have been seeing the low utilization because of a problem with the threading model used by the programmers. They're using user threads as opposed to kernel threads and are seeing limitations in what user threads are allowed to do.