When applications stall (or when Windows is slow), is it because of processing or swapping?

[Antoneo]

I'm curious to the behavior of Windows (and other OSes) when there is "high load on the computer." We all know that when we have an intensive program (heavy filtering in photoshop or rendering in Premiere or 3DStudio Max) that you can't do much else (single processor machine). Sometimes the applications even seem to have stalled, and then you get the "Program not responding..." message. Is it usually because of swapping from memory to hard drive and vice versa or is it a simple case of not enough CPU power, and a particular application is just stuck in it? A bit of both? Generally speaking that is.

 

[Nothinman]

Generally it should not be CPU as the OS should schedule other programs in a pretty fair fashion. If you mean to say that the program that isn't responding is also the one using all of the CPU, well that's probably a design issue with that specific program. That program should either check for window messages periodically so that it's UI can be redrawn or it should put the processing into a seperate thread from the processing so that both can run at the same time.

As long as you have a decent amount of memory paging to and from disk (there is no swapping done these days) should only cause a minimal delay and it should be obvious because of the disk activity.