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I've noticed that some applications (often games) have a very high number of page faults; for example, Diablo III can get into the range of 2 million within 30 minutes of play.

Why is this? Does something other than the OS needing a page that isn't in physical memory cause a page fault? Why am I seeing 2 million page faults when I have 3-4 GB of RAM free, shouldn't the operating system be able to keep everything paged in?

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It could be a memory mapped file. It's not necessarily a bad thing. – Oliver Salzburg May 20 '12 at 20:46
Also, you get a page fault each time a new block of virtual memory is allocated. In particular this means you get at least one page fault for every new thread, when the stack is allocated. So if a program either creates lots of short-lived threads or allocates and releases memory often, you'll get a high page fault count. – Harry Johnston May 20 '12 at 22:35

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