What Is Thrashing: How Memory Overload Cripples System Performance

Thrashing is a computing condition where a system wastes most of its resources swapping data in and out of memory rather than performing useful work. It occurs in operating systems when too many processes compete for limited RAM, causing continuous page faults and heavy disk I/O that starves the CPU of productive time. The same problem can affect caching layers like Redis, where a cache too small for its workload repeatedly evicts and reloads the same data, resulting in constant cache misses and unnecessary database queries. Common warning signs include high CPU usage with low throughput, elevated page-fault rates, and poor cache hit ratios. Prevention strategies include increasing physical memory or cache size, reducing the number of concurrent processes, and adopting smarter replacement algorithms such as LRU or LFU.