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Memcached evicts items despite free RAM because its slab allocator rounds values to fixed chunk sizes. Learn to read stats slabs, spot per-class starvation, and use slab_automove or manual reassignment to reclaim wasted pages.
Learn how to choose Memcached chunk size and growth factor to avoid premature evictions, reduce internal fragmentation, and validate slab health with stats slabs.
When a stored value exceeds memcached's item size limit, the text-protocol storage path rejects the write with SERVER_ERROR object too large for cache . The default limit is 1 MB, it can only be changed at daemon startup with the -I option, and the maximum permitted value is version- and build-dependent. The unresolved decision is whether to raise -I or to k
Observed behavior On memcached 1.6.x running with the default slab allocator, resident memory climbs as slab classes grow to accommodate peak item sizes, but after large-scale eviction or expiration the process RSS stays at its high-water mark. The bytes stat from stats falls as expected, yet the OS-visible memory footprint does not. This is distinct from th
Optimizing Memcached Memory Distribution Memcached manages memory through a Slab Allocator to prevent fragmentation, grouping items of similar sizes into specific slabs. When a slab reaches capacity, the system triggers LRU eviction for that specific slab, regardless of whether memory is available in other slabs. To mitigate premature evictions and improve h
SERVER_ERROR out of memory in slab allocator Memcached's slab allocator divides memory into fixed-size chunks grouped into slab classes. Once a page is assigned to a specific slab class it cannot be reassigned to another class during the daemon's lifecycle. A shift in stored item sizes can exhaust one slab class while other classes retain free memory. In tha
memcached