remap_file_pages - 創建一個非線性映射文件

內容簡介

#include <sys/mman.h>

int remap_file_pages(void **start*, size_t size**, int** prot**,** ssize_t pgoff**, int** flags**);**

描述

remap_file_pages () 系統調用是用來建立一個非線性映射，也就是，在該文件的頁被映射到存儲器中的非連續的順序映射 . The advantage of using  remap_file_pages () over using repeated calls to  mmap (2) is that the former approach does not require the kernel to create additional VMA (Virtual Memory Area) data structures.

要創建一個非線性映射，我們執行以下步驟：

標籤

描述

1.

Use mmap() to create a mapping (which is initially linear). This mapping must be created with the MAP_SHARED flag.

2.

Use one or more calls to remap_file_pages() to rearrange the correspondence between the pages of the mapping and the pages of the file. It is possible to map the same page of a file into multiple locations within the mapped region.

The  pgoff  and  size  arguments specify the region of the file that is to be relocated within the mapping:  pgoff  is a file offset in units of the system page size;  size  is the length of the region in bytes.

The start argument serves two purposes. First, it identifies the mapping whose pages we want to rearrange. Thus, start must be an address that falls within a region previously mapped by a call to mmap(). Second, start specifies the address at which the file pages identified by pgoff and size will be placed.

The values specified in start and size should be multiples of the system page size. If they are not, then the kernel rounds both values down to the nearest multiple of the page size.

The prot argument must be specified as 0.

The flags argument has the same meaning as for mmap(), but all flags other thanMAP_NONBLOCK are ignored.

返回值

On success,  remap_file_pages () returns 0. On error, -1 is returned, and  errno  is set appropriately.

注意

The  remap_file_pages () system call appeared in Linux 2.5.46.

錯誤

標籤

描述

EINVAL

start does not refer to a valid mapping created with theMAP_SHARED flag.

EINVAL

start, size, prot, or pgoff is invalid.

遵循於

The  remap_file_pages () system call is Linux specific.

另請參閱

• getpagesize (2)

• mmap (2)

• mmap2 (2)

• mprotect (2)

• mremap (2)

• msync (2)