Buffer Resources

The buffer cache for read and write system calls uses a range of virtual addresses in the kernel address space. A page of data is mapped into the kernel address space and the amount of data requested by the process is then physically copied to the process' address space. The page is then unmapped in the kernel. The physical page will remain in memory until the page is freed up by the page daemon.

This means a few I/O-intensive processes can monopolize or force other processes out of main memory. To prevent monopolization of main memory, balance the running of I/O-intensive processes serially in a script or with the at command. Programmers can use mmap(2) and madvise(3) to ensure that their programs free memory when they are not using it.