карта страниц памяти (map pages of memory)
Использование в приложениях (Application usage)
Use of mmap() may reduce the amount of memory available to other
memory allocation functions.
Use of MAP_FIXED may result in unspecified behavior in further
use of malloc() and shmat(). The use of MAP_FIXED is
discouraged, as it may prevent an implementation from making the
most effective use of resources. Most implementations require
that off and addr are multiples of the page size as returned by
sysconf().
The application must ensure correct synchronization when using
mmap() in conjunction with any other file access method, such as
read() and write(), standard input/output, and shmat().
The mmap() function allows access to resources via address space
manipulations, instead of read()/write(). Once a file is mapped,
all a process has to do to access it is use the data at the
address to which the file was mapped. So, using pseudo-code to
illustrate the way in which an existing program might be changed
to use mmap(), the following:
fildes = open(...)
lseek(fildes, some_offset)
read(fildes, buf, len)
/* Use data in buf. */
becomes:
fildes = open(...)
address = mmap(0, len, PROT_READ, MAP_PRIVATE, fildes, some_offset)
/* Use data at address. */
