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Special Forums Hardware Filesystems, Disks and Memory mmap
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Old 07-30-2002

Hello. I'm writing some random access i/o software on Solaris 8 using mmap64 to memory map large files (my test file is ~25 GB).

The abbreviated code fragment is:

fd = open(cbuf,O_RDONLY|O_LARGEFILE);

struct stat statbuf;

off_t len = (off_t)statbuf.st_size; // len = 24974764635

map_ptr = (char *)mmap64(NULL,len,

madvise(map_ptr,len,MADV_DONTNEED | MADV_RANDOM);

I think the problem may be mmap's 2nd argument which is (size_t) intead of (off_t) because I only have access up to 3.5 GB, which is about the value of the bottom 32 bytes of len.

Any help you can provide will be greatly appreciated.

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MMAP2(2)						     Linux Programmer's Manual							  MMAP2(2)

mmap2 - map files or devices into memory SYNOPSIS
#include <sys/mman.h> void *mmap2(void *addr, size_t length, int prot, int flags, int fd, off_t pgoffset); DESCRIPTION
The mmap2() system call operates in exactly the same way as mmap(2), except that the final argument specifies the offset into the file in 4096-byte units (instead of bytes, as is done by mmap(2)). This enables applications that use a 32-bit off_t to map large files (up to 2^44 bytes). RETURN VALUE
On success, mmap2() returns a pointer to the mapped area. On error -1 is returned and errno is set appropriately. ERRORS
EFAULT Problem with getting the data from userspace. EINVAL (Various platforms where the page size is not 4096 bytes.) offset * 4096 is not a multiple of the system page size. mmap2() can return any of the same errors as mmap(2). VERSIONS
mmap2() is available since Linux 2.3.31. CONFORMING TO
This system call is Linux-specific. NOTES
Nowadays, the glibc mmap() wrapper function invokes this system call rather than the mmap(2) system call. On ia64, the unit for offset is actually the system page size, rather than 4096 bytes. SEE ALSO
getpagesize(2), mmap(2), mremap(2), msync(2), shm_open(3) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at Linux 2008-04-22 MMAP2(2)