awesomeITguy :
Thanks for answering me so quickly. I have an updated picture to reference. My cache doesn't ever ]decrease by much and I've never seen it end up in the available memory........
Am I going crazy or is something wrong? I have a brand new server, that crashed last week, this is why I'm so worried.....
Nothing is wrong. The cache won't decrease on its own.
Physical memory is considered to be a scarce resource. It's also a use-it-or-lose-it resource. It's very wasteful to have fast physical memory just sitting there doing nothing, so the operating system fills it with a cache. This cache can be invalidated very quickly when a process needs memory.
"Available" is the amount of physical memory that is available to be allocated to a process
right now without performing any disk access. It's also approximately the sum of cached + free - reserved - modified. The OS will always keep some quantity of memory in reserve, usually around 64MiB or so. Modified memory is cached memory that has been released by all processes but it contains write-back cached data that needs to be written to a separate backing store such as a hard disk first.
As soon as a process terminates or returns memory to the operating system that freed up memory is returned to the free pool from which it will either be allocated to another process or filled with a cache.
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