JVM Page Faults should be Zero, right? How High is OK?

OK folks, this is another "I think is a stupid question", but for clarity's sake warrants appearing foolish.

In the windows task manager for a properly-configured JVM, the page fault should be Zero right? (or "top" for linux folks)

e.g., if your Xmx says "4G" and the JVM has 4G of physical RAM available (e.g. out of total 8G, leaving 3+G for the OS), the OS should never reach into pagefile.sys for normal jvm operations.

That's the theory. What's the practice?开发者_如何学运维 And if pagefaults are non-zero, what's an acceptable number?

Monitoring Tools

What's the best way to monitor for 'page faults too high' ?

thanks

Even if you allocate a large amount of memory for the JVM heap, page faults can still occur. For example, if you try to load a file which is on a hard disk but not mapped into RAM a page fault occurs and the file is paged into memory.