高手进 - 共享内存算作cache， 还能不能在被使用？

ccj_19850121

比如一台16G linux机器, 一个进程分配10G共享内存, 在free里面算作cache的， 那当系统内存不足时， 是否可以使用这10G的cache?

Shell_HAT

可以。RedHat官网说明：

$ free
              total       used        free    shared    buffers    cached
Mem:        4040360    4012200       28160         0     176628   3571348
-/+ buffers/cache:      264224     3776136
Swap:       4200956      12184     4188772

In this example the total amount of available memory is 4040360 KB. 264224 KB are used by processes and 3776136 KB are free for other applications. Do not get confused by the first line which shows that 28160KB are free! If you look at the usage figures you can see that most of the memory use is for buffers and cache. Linux always tries to use RAM to speed up disk operations by using available memory for buffers (file system metadata) and cache (pages with actual contents of files or block devices). This helps the system to run faster because disk information is already in memory which saves I/O operations. If space is needed by programs or applications like Oracle, then Linux will free up the buffers and cache to yield memory for the applications. If your system runs for a while you will usually see a small number under the field "free" on the first line.