Clean system cache and free memory under Linux

When linux After reading files frequently , Physical memory will soon run out , When the program is finished , Memory will not be released normally , But all the time caching, Therefore, it is necessary to manually clean up the system cache to free memory .

sync

The operating system is running , The accessed files will be placed in buffer in . To avoid power failure , Data loss caused by faults such as , We need to take buffer Cache data in is written to disk

> sync;sync;sync

Do it manually sync command （ describe ：sync The command runs sync Subroutines . If you have to stop the system , Then run sync Command to ensure file system integrity .sync Command to write all unwritten system buffers to disk , Include modified i-node、 Delayed block I/O And read-write mapping files

Manual memory release command

> echo 3>/proc/sys/vm/drop_caches

drop_caches The value of can be 0-3 Number between , It means different things ：0： Don't release （ System default ） 1： Free page cache 2： Release dentries and inodes

Look at the memory

> free -h

total—— Total physical memory 
used—— Used memory , Generally, this value will be relatively large , Because this value includes cache+ Memory used by the application 
free—— Completely unused memory 
shared—— Application shared memory 
buffers—— cache , It's mainly used for catalogues ,inode It's worth waiting for （ls Large directories can see this value increase ）
cached—— cache , For open files 

Restore default settings

Caching can improve the efficiency of the system , If you find that the system memory is often insufficient , You should consider adding memory , Instead of cleaning up often

> echo 0>/proc/sys/vm/drop_caches

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