What Is a Page Fault?
A page fault is the event the hardware raises when a process touches a virtual memory page that is not presently mapped to physical memory. The kernel handles it by mapping a new page, loading data from disk, or copying a shared page, then resumes the instruction. Most faults are routine, but excessive faulting from swapping signals memory pressure.
Why it matters
A flood of page faults that pull pages from disk, known as thrashing, can make a memory-starved CI job crawl. Watching fault rates helps distinguish genuine CPU work from time lost to memory pressure.
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