The rate at which page fault occurs is known as __________.

In demand-paging systems, a page fault occurs whenever a running process references a page that is not currently resident in main memory, forcing the OS to fetch it from secondary storage. As long as a process has enough frames for its working set, faults stay infrequent. When a process (or the whole system) is starved of frames, the OS ends up servicing faults back-to-back, and the specific named state in which the CPU spends more time handling these faults than executing processes — collapsing throughput even while the system looks 'busy' — has its own distinct term in OS terminology, separate from the general mechanisms of paging, swapping, or compaction.

Applying this to the blank: it is asking for the name of that very-high-page-fault-rate condition, not for the paging mechanism itself. That condition is thrashing — the CPU is almost entirely occupied moving pages in and out of memory, so real process execution nearly stalls.

• swapping — moves an entire process (not individual pages) between memory and disk; it names a mechanism, not a fault-rate condition.

• paging — the memory-allocation scheme of dividing memory into fixed-size blocks; it is the reason faults can happen, not the term for their rate being high.

• compaction — relocates memory contents to consolidate free space and cut external fragmentation; it has nothing to do with fault frequency.

So the term for an excessively high rate of page faults is thrashing.