redis.memory.fragmentation_ratio

Ratio of RSS (resident set size) memory to used memory, indicating memory fragmentation. Values >1.5 suggest significant fragmentation where allocated memory exceeds actively used memory due to allocator inefficiency. High fragmentation wastes memory and can trigger OOM conditions even when logical memory usage seems acceptable. This amplifies cache eviction pressure as described in the fragmentation insight — Redis may evict keys unnecessarily because fragmented memory appears fuller than it actually is.