In Linux, mem is physical memory; when the physical memory is about to overflow, the infrequently used memory in the memory will be transferred to SWAP, and will be transferred back after the physical memory is free and the SWAP memory is active.
#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.
mem is physical memory. When the physical memory is about to overflow, the infrequently used memory in the memory will be transferred to SWAP until the physical memory is free, and the swap memory Transfer it back after it becomes active
Linux mem/swap/buffers/cached difference
The free command provides a more concise view of system memory usage compared to top:
# free -m
mem: Indicates physical memory statistics
buff/cache: Indicates cache statistics of physical memory
swap: Indicates the usage of the swap partition on the hard disk
The currently available memory of the system is not marked by free in the first line. It only represents unallocated memory.
The buffer/cache column is too high
## What is the main purpose of #buff/cache? Linux has an advanced caching mechanism, which will target dentry (used in VFS-virtual file system to accelerate the conversion of file path names to inodes), buffer cache (for reading and writing disk blocks) and page cache ( Perform caching operations for file inode reading and writing to improve reading and writing efficiency. However, after a large number of file operations are performed, the cache will basically use up the memory resources. Although the file reading efficiency is improved, the physical memory will be gradually used up. It turns out that the system performs frequent file reading and writing operations, but why does the operating system not actively recycle? It turns out that the default parameter setting of drop_caches is not to release. The value of drop_caches can be a number between 0-3, representing different meanings: 0: Do not release (system default value) 1: Release the page cache 2: Release dentries and inodes3: Release all cachesModification:# echo 1 > /proc/sys/vm/drop_caches
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