A memory access branches to minor-fault work in memory, major-fault page-in I/O, or invalid-access handling. Fault counts do not count all storage requests.

A page fault is not always a storage read

A page fault means the processor could not complete an access using the current mapping or permissions. It is not synonymous with a storage read, and some faults represent invalid accesses rather than recoverable demand paging. Linux’s minor and major counters distinguish whether handling required page-in I/O. Interpret those counters alongside the mapping type and workload; neither is a direct measurement of all application storage traffic. ...

November 13, 2027 · 5 min · XB Field Notes