page_cache_sync_readahead(9) [centos man page]

PAGE_CACHE_SYNC_READ(9) 				    Memory Management in Linux					   PAGE_CACHE_SYNC_READ(9)

NAME

       page_cache_sync_readahead - generic file readahead

SYNOPSIS

       void page_cache_sync_readahead(struct address_space * mapping, struct file_ra_state * ra, struct file * filp, pgoff_t offset,
				      unsigned long req_size);

ARGUMENTS

       mapping
	   address_space which holds the pagecache and I/O vectors

       ra
	   file_ra_state which holds the readahead state

       filp
	   passed on to ->readpage and ->readpages

       offset
	   start offset into mapping, in pagecache page-sized units

       req_size
	   hint: total size of the read which the caller is performing in pagecache pages

DESCRIPTION

       page_cache_sync_readahead should be called when a cache miss happened: it will submit the read. The readahead logic may decide to piggyback
       more pages onto the read request if access patterns suggest it will improve performance.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014						   PAGE_CACHE_SYNC_READ(9)

READAHEAD(2)						     Linux Programmer's Manual						      READAHEAD(2)

NAME

       readahead - perform file readahead into page cache

SYNOPSIS

       #define _GNU_SOURCE	       /* See feature_test_macros(7) */
       #include <fcntl.h>

       ssize_t readahead(int fd, off64_t offset, size_t count);

DESCRIPTION

       readahead()  populates  the  page  cache  with data from a file so that subsequent reads from that file will not block on disk I/O.  The fd
       argument is a file descriptor identifying the file which is to be read.	The offset argument specifies the starting point from  which  data
       is  to  be read and count specifies the number of bytes to be read.  I/O is performed in whole pages, so that offset is effectively rounded
       down to a page boundary and bytes are read up to the next page boundary greater than or equal to (offset+count).  readahead() does not read
       beyond  the end of the file.  readahead() blocks until the specified data has been read.  The current file offset of the open file referred
       to by fd is left unchanged.

RETURN VALUE

       On success, readahead() returns 0; on failure, -1 is returned, with errno set to indicate the cause of the error.

ERRORS

       EBADF  fd is not a valid file descriptor or is not open for reading.

       EINVAL fd does not refer to a file type to which readahead() can be applied.

VERSIONS

       The readahead() system call appeared in Linux 2.4.13; glibc support has been provided since version 2.3.

CONFORMING TO

       The readahead() system call is Linux-specific, and its use should be avoided in portable applications.

SEE ALSO

       lseek(2), madvise(2), mmap(2), posix_fadvise(2), read(2)

COLOPHON

       This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2010-09-10							      READAHEAD(2)