Login or Register to Ask a Question and Join Our Community


Filesystems, Disks and Memory

mmap

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Special Forums Hardware Filesystems, Disks and Memory mmap
# 1  
Old 07-30-2002
mmap
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;
fstat(fd,&statbuf);

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

map_ptr = (char *)mmap64(NULL,len,
PROT_READ,
MAP_NORESERVE|MAP_SHARED,
fd,0);

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.

Thanks,
gusm
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. BSD

Mmap source

I'm new to kernels and C, and I am tinkering around trying to understand OpenBSD's secure memory management. I'm stumped on a couple points. I've read up on malloc() which was apparently modified years ago to allocate memory using mmap. First question, that would be this here, right? ... (4 Replies)
Discussion started by: dcicc
4 Replies

2. Emergency UNIX and Linux Support

mmap

I want to know whether this is possile or ever been tried out. I want to obtain a chuck of memory using mmap() I do it so : n = mmap(0, 8000, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); And hold on to that memory, when a process requests for memory, some memory is... (2 Replies)
Discussion started by: xerox
2 Replies

3. UNIX for Advanced & Expert Users

Regarding MMAP, MLOCK etc..

Hi I want to lock or prevent a portion of memory which I allocated. So I tried MLOCK, MPROTECT and some like this. But all these functions works only on page border. Can I know why that so. Is that possible to protect a portion of memory which is in middle of the page. Example. int A; ... (1 Reply)
Discussion started by: jionnet
1 Replies

4. Programming

mmap

hai, How do we map 'n' number of files into memory by using mmap system call?? Thanks in advance...... (5 Replies)
Discussion started by: andrew.paul
5 Replies

5. Homework & Coursework Questions

mmap

Descriptions: Develop a program that uses mmap() to map a file to memory space. Prepare such a file by yourself and do the follows. <LI class=MsoNormal>Display the content of the file after mapping; <LI class=MsoNormal>Output how many digits included in the file; <LI class=MsoNormal>Replace... (1 Reply)
Discussion started by: gokult
1 Replies

6. Programming

mmap()

how to use mmap() to map a file to memory space. Do you have any simple program???? Because I have to implement lot of concepts into it. (5 Replies)
Discussion started by: gokult
5 Replies

7. UNIX for Dummies Questions & Answers

mmap()

how to use mmap() to map a file to memory space. Do you have any simple program???? Because I have to implement lot of concepts into it. (3 Replies)
Discussion started by: gokult
3 Replies

8. Solaris

mmap() on 64 bit m/c

Dear Experts, i have a problem related to mmap(), when i run my program on sun for 64 bit which is throwing SIGBUS when it encounters mmap() function, what is the reason how to resolve this one, because it is working for 32 bit. with regards, vidya. (2 Replies)
Discussion started by: vin_pll
2 Replies

9. UNIX for Advanced & Expert Users

mmap and select

I'm using select() to monitor multiple file descriptors (inet sockets) in application. But this application must also collaborate with other applications on the same host via shared memory (mmap'ed file) due to performance reasons. How can I become notification that mmaped memory is changed or... (1 Reply)
Discussion started by: Hitori
1 Replies

10. HP-UX

mmap failed

We recently have been seeing the following type of error on our development server. Being somewhat new to HP-UX I was hoping to get some insight. Here is what I have found. I have been doing some research. /usr/lib/dld.sl: Call to mmap() failed - TEXT /u07/mdev/lib/libCLEND.sl... (2 Replies)
Discussion started by: scotbuff
2 Replies
Login or Register to Ask a Question

LEARN ABOUT XFREE86

mmap2

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

NAME

       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

       This  is  probably  not	the  system call that you are interested in; instead, see mmap(2), which describes the glibc wrapper function that
       invokes this system call.

       The mmap2() system call provides the same interface 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 user space.

       EINVAL (Various platforms where the page size is not 4096 bytes.)  offset * 4096 is not a multiple of the system page size.

       mmap2() can also return any of the errors described in mmap(2).

VERSIONS

       mmap2() is available since Linux 2.3.31.

CONFORMING TO

       This system call is Linux-specific.

NOTES

       On architectures where this system call is present, the glibc mmap() wrapper function invokes this system call rather than the mmap(2) sys-
       tem call.

       This system call does not exist on x86-64.

       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 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux								    2017-09-15								  MMAP2(2)