free - Linux tools 2 of n

最新推荐文章于 2024-09-16 00:45:29 发布

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本文详细解析了Linux系统使用free命令获取的内存信息，包括总内存、已用内存、空闲内存等关键指标，并解释了各部分的具体含义及相互关系。

"free" is used to check the system's memory information.

Let's understand its output.

sysadmin@ubuntu:~$ free
total used free shared buffers cached
Mem: 2047900 1169720 878180 0 87280 951716
-/+ buffers/cache: 130724 1917176
Swap: 2094076 0 2094076

The second line (Mem:)
total 2047900: is the total physical memory in the system (subtracts some overhead)
used 1169720: is the used physical memory in the system
free 878180: is the free physical memory in the system

total = used + free

buffers 87280: buffer memory (usually used by kernel for block io etc and usually is relative small). Can be freed by kernel if usable physical memory is really low.
cached 951716: disk data page cached in memory. Can be freed by kernel if usable physical memory is really low.

The third line (-/+ buffers/cache:)
used 130724 = (used 1169720 - buffers 87280 - cached 951716) in the second (Mem:) line (this is why it is using "-" in "-/+ buffers/cache")
free 1917176 = (free 878180 + buffers 87280 + cached 951716) in the second (Mem:) line (this is why it is using "+" in "-/+ buffers/cache")
"buffers and cached" is potentially able to be recycled, this is why free count them as free.