Original article:Does the screenshot below from New Relic look familiar to you? Let’s say you have a web server with 2GB of RAM or maybe 256GB. If things change in the future, we only have to change it in one place…” – Source

It is more convenient to provide such an estimate in /proc/meminfo.

However, this may change in the future, and user space really should not be expected to know kernel internals to come up with an estimate for the amount of free memory. It does not include reclaimable slab memory, which can take up a large fraction of the system memory on mostly idle systems with lots of files.Ĭurrently, the amount of memory that is available for a new workload, without pushing the system into swap, can be estimated from MemFree, Active(file), Inactive(file), and SReclaimable, as well as the “low” watermarks from /proc/zoneinfo. It is wrong because Cached includes memory that is not freeable as page cache, for example, shared memory segments, tmpfs, and ramfs. They generally do this by adding up “free” and “cached,” which was fine ten years ago but is pretty much guaranteed to be wrong today. : /proc/meminfo: provide estimated available memory: “Many load balancing and workload placing programs check /proc/meminfo to estimate how much free memory is available. Unlike the data provided by the cache or free fields, this field takes into account page cache and also that not all reclaimable memory slabs will be reclaimed due to items being in use (MemAvailable in /proc/meminfo, available on kernels 3.14, emulated on kernels 2.6.27+, otherwise the same as free).” “Estimation of how much memory is available for starting new applications, without swapping. As outlined here, memory is now marked as available by the Linux kernel:

Ubuntu monitor ram usage