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 ker‐ nels 2.6. Shared Memory used (mostly) by tmpfs (Shmem in /proc/meminfo, available on kernels 2.6.32, dis‐īuffers Memory used by kernel buffers (Buffers in /proc/meminfo)Ĭache Memory used by the page cache and slabs (Cached and Slab in /proc/meminfo)Īvailable Estimation of how much memory is available for starting new applications, without swap‐ ping. The free command shows amount of free and used memory in the Linux system. Used Used memory (calculated as total - free - buffers - cache)įree Unused memory (MemFree and SwapFree in /proc/meminfo) The calloc () function allocates memory for an array of nmemb elements of size bytes each and returns a pointer to the allocated memory. Total Total installed memory (MemTotal and SwapTotal in /proc/meminfo) The information is gathered by parsing /proc/mem‐ So, when your RAM is full, the Operating System can off-load parts of it currently not used data to disk, therefore free up memory for application that needs it.įree displays the total amount of free and used physical and swap memory in the system, as wellĪs the buffers and caches used by the kernel. Virtual memory means the perm storage is used as temp space for RAM. Although the free command may show that a particular system does not have much free memory, this is not necessarily bad. The virtual memory on hard-disk is called swap space. Linux uses non-volatile storage device (example: hard-disk, flash-memory) as virtual memory. Swap is the disk space used for virtual memory purposes. (Because RAM's IO speed is a thousand times faster than hard disk, so Operating System will load disk data to RAM as cache) Server B: still wasting 30GB of memory (free) after 153 days of uptime. Server A: Less than 1 free memory (wasted memory), 13GB free memory. I also ran the uptime command to confirm that both systems have been online for a while. Linux uses RAM as cache for file data (from hard-disk). The result should look similar to these two screenshots below.
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