memleft

Memleft is a term used in computing to describe the amount of free memory remaining in a system, process, or runtime environment after accounting for current allocations. It is typically expressed in bytes or higher-level units such as megabytes or gigabytes and can be measured at different scopes, including system-wide, per-process, or per-container levels. Memleft is a practical metric for capacity planning, monitoring, and adaptive resource management, but it is not a single universal indicator; its interpretation depends on what memory is included in the calculation (for example, whether caches, buffers, and memory-mapped regions are counted as available or not).

In operating systems and runtime environments, memleft informs memory reclamation decisions such as garbage collection, paging, and swapping. For managed runtimes, memleft-based heuristics may trigger collection cycles before memory pressure becomes critical. In cloud and container deployments, memleft is commonly exposed by monitoring tools to enforce memory limits, drive auto-scaling, or initiate throttling when available memory falls below predefined thresholds.

Because memleft can be affected by factors like caches, buffers, and deferred deallocation, it is important to interpret it carefully and in context. A low memleft value does not always imply immediate failure, but it often signals increased risk of contention or performance degradation if memory is not reclaimed promptly. The term is descriptive and widely used in dashboards and documentation, though it is not standardized across platforms.

See also: memory management, garbage collection, memory pressure, paging, containerization.