# free

The results are as follows :

Mem: Represents physical memory statistics

total Total memory 8057964KB
used Used memory 7852484KB
free The amount of free memory 205480KB
shared It has been abandoned , Always 0
buffers Buffer Number of cache memory : 290432KB
cached Page Number of cache memory :5735024KB
( There is relationship between : total = used + free )

-/+ buffers/cached: Represents the cache statistics of physical memory

(-buffers/cache) used Memory count :1827028KB ( The first part of Mem In a row used - buffers - cached)
(+buffers/cache) free Memory count : 6230936KB ( The first part of Mem In a row free + buffers + cached)

-buffers/cache It reflects the memory actually eaten by the program ;
+buffers/cache It reflects the total amount of memory that can be misappropriated ;

Swap: Indicates the usage of the swap partition on the hard disk

free Parameter description
-m With M Check memory usage for units ( The default is kb)
-b With Byte Check memory usage for units
-k With KB Check memory usage for units
-o Do not display cache tuning Columns
-t Display memory sum column
-V Display version information
-s < Seconds apart > You can not simply monitor the memory usage within a specified period of time

buffers And cached The difference between
For applications ,buffers/cached Is equal to available ,
because buffer/cached To improve the performance of file reading ,
When the application needs to use memory ,buffer/cached It will be recycled soon .
So from an application perspective Available memory = System free memory+buffers+cached.

buffers It refers to the buffer size used for block devices ,
He only records the file system metadata as well as tracking in-flight pages.
cached It's used to buffer files .
That is to say :buffers It's for storing , What's in the catalog , Permissions, etc. .
and cached It's directly used to remember the files we opened , If you want to know if it really works ,
You can try it , Two orders in succession #man X , You can obviously feel that the second start was much faster .

Remember that memory is for use , Not to see . Unlike windows, No matter how much physical memory you have , He's always swapping hard drives for File to read .

This is the same. windows Why often prompt the reason that fictitious space is insufficient . Think about it , How boring , There's a lot more in memory When , Take out a part

Hard disk space to act as memory . Hard disk is faster than memory . So let's see linux, As long as no need swap In exchange for Space , You don't have to worry about your memory

too little . If often swap Use a lot , Maybe you should consider adding physical memory . This is also linux see The standard of whether the memory is enough .

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