This read-only integer reports the number of pages being swapped in from swap files in response to a major page fault. An admin uses this page-granular counter, alongside the byte-rate swap-in object, to more precisely quantify how many individual page-fault-driven swap-ins are occurring. For example, a high page-swap-in rate combined with degraded application response times would confirm to an admin that major page faults, not just general memory churn, are the specific cause of the slowdown.