Memory available in Linux

In Linux, you can enter the free command to obtain the current { Tagshow (Event) } "> System memory usage. # Busybox free Total used free shared Buffers Mem: 55636 52808 2828 0 3132 Swap: 0 0 0 Total: 55636 52808 2828 When I typed the above command with joy, I received a burst of cold sweat, 2828 kb. My system only has more than 2 MB of memory. Can the system still run, is there a command error !!! Let's take a look at what the results look like in a Linux system on a PC. # Free Total used free shared buffers cached Mem: 4091524 4021016 70508 0 7656 1824312 -/+ Buffers/cache: 2189048 1902476 Swap: 4088532 2891732 1196800 Here I will explain several key concepts first. Buffers: it is mainly used to buffer Block devices in Linux. Cached: Used to buffer { Tagshow (Event) } "> File. Memory is a very valuable resource in the system. Linux uses memory to cache some files if the memory is sufficient and you do not need to use it for whitelist. This speeds up the process; when the memory is insufficient, the memory will be recycled again { Tagshow (Event) } "> Program usage. Therefore, the real available memory is free + buffers + cached = 70508 + 7656 + 1824312 = 1902476. In this way, we know that busybox has a defect in implementing free. It lacks a key column of cache, so we cannot obtain the exact idle memory value. Since the free command does not work, our focus is on the free { Tagshow (Event) } "> Where did the data come from! The answer is:/proc /Proc { Tagshow (Event) } "> A directory is a special file system that does not occupy disk space { Tagshow (Event) } "> User request information, generated in real time by the Linux kernel. Therefore, we can access some data in the Linux Kernel through the proc directory. We can obtain the memory usage of the current system from the meminfo file in the proc directory. # Cat/proc/meminfo Memtotal: 55880 KB Memfree: 2252 KB Buffers': 3760 KB Cached: 26112 KB Swapcached: 0 KB Active: 34652 KB Inactive: 8716 KB Hightotal: 0 KB Highfree: 0 KB Lowtotal: 55880 KB Lowfree: 2252 KB Swaptotal: 0 KB Swapfree: 0 KB Dirty: 0 KB Writeback: 0 KB Mapped: 34220 KB Slab: 4504 KB Commitlimit: 27940 KB Committed_as: 109704 KB Pagetables: 1876 KB Vmalloctotal: 196608 KB Vmallocused: 2360 KB Vmallocchunk: 4112384 KB From the above results, we can know that the system currently has a total of K physical memory, Where Free 2252kb Buffers 3760 KB Cached 26112 KB So the current available physical memory = 2252 + 3760 + 26112 = 32124kb, it should be said that there are still a lot. At last, we had a hard time getting the available system memory, which makes it easy to calculate Physical memory used = 55880-32124 = 23756kb