Very Computer

I need to mmap() a large file (between 2GB and 3GB)
on Solaris 2.6. I thought that using
-D_LARGEFILE64_SOURCE and -D_FILE_OFFSET_BITS=64
would do the job. But no - I get an ENOMEM error
from mmap(), even on a small program which only mmaps
this one file. The same binary works fine on Solaris 8.

The same error occurs if I use the explicit largefile
interfaces open64(), mmap64(), -D_FILE_OFFSET_BITS=64.

(I'm using SunOS Generic_105181-21 sun4u sparc
SUNW,Ultra-Enterprise.)

Am I doing something wrong, or is this a bug in Solaris 2.6?
If the latter, is there a patch available?

TIA.

- MikeM.

Quote:> would do the job. But no - I get an ENOMEM error
> from mmap(), even on a small program which only mmaps
> this one file. The same binary works fine on Solaris 8.

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Quote:>   >> would do the job. But no - I get an ENOMEM error
>   >> from mmap(), even on a small program which only mmaps
>   >> this one file. The same binary works fine on Solaris 8.

>  > Do you have enough swap space?

When the app restarts, it attempts to mmap the entire
file since that's easier. But this fails with the
error described above. So it definitely seems related
to the attempt to mmap 2GB+ as a single contiguous
region. I suppose I could rework my app code to mmap
in smaller segments on restart, but I figured I should
find out first whether there's a patch for Solaris 2.6.

- MikeM.

Casper
--
Expressed in this posting are my opinions.  They are in no way related
to opinions held by my employer, Sun Microsystems.
Statements on Sun products included here are not gospel and may
be fiction rather than truth.

00010000      8K read/exec         dev:196,267 ino:3846621
00020000      8K read/write/exec   dev:196,267 ino:3846621
00022000      8K read/write/exec     [ heap ]
6F400000 2097152K read/shared       dev:196,267 ino:3846620
EF600000    592K read/exec         /usr/lib/libc.so.1
EF6A2000     32K read/write/exec   /usr/lib/libc.so.1
EF6AA000      8K read/write/exec     [ anon ]
EF6D0000     16K read/exec         /usr/platform/sun4u/lib/libc_psr.so.1
EF6F0000      8K read/write/exec     [ anon ]
EF700000      8K read/exec         /usr/lib/libdl.so.1
EF710000    248K read/exec         /usr/lib/libC.so.5
EF75C000     40K read/write/exec   /usr/lib/libC.so.5
EF766000     56K read/write/exec     [ anon ]
EF780000     88K read/exec
/export/common/opt/SUNWspro/WS6/lib/libm.so.1
EF7A4000      8K read/write/exec
/export/common/opt/SUNWspro/WS6/lib/libm.so.1
EF7B0000      8K read/exec         /usr/lib/libw.so.1
EF7C0000    128K read/exec         /usr/lib/ld.so.1
EF7EE000     16K read/write/exec   /usr/lib/ld.so.1
EFFFC000     16K read/write/exec     [ stack ]
 total  2098448K

(My mmapped file is the 4th entry from the top.)
See how there's still almost 2GB of *unused* address space?
But when I change my program to use a file of exactly 2GB,
it fails with the error described above.

A listing of the test program appears below.

- MikeM.

//============================================================================

// large_mmap.cc
//
// This C++ program creates a large file and attempts to mmap it. It
sleeps
// for 30 secs, then unmaps and removes the file. All file operations are

// performed with the largefile interface.
//
// The purpose of this program is to investigate file size limitations of

// mmap64() under Solaris 2.6.
//
// Compile using -D_FILE_OFFSET_BITS=64
//============================================================================

#include <iostream.h>

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/types.h>
//============================================================================

main()
{
    static char const * const  filename = "thefile";

    unlink(filename);

    int  fd = open64(filename, O_RDWR|O_CREAT, 0664);

    if (fd == -1)
    {
        perror(filename);
        cerr << "Couldn't open64(\"" << filename << "\")\n";
        return 1;
    }

    size_t const  twoGB = 2147483648u;

    size_t const  filelen = twoGB;   // mmap64 fails if >= twoGB,
                                     // but changing to (twoGB - 1)
                                     // works ok.

    cout << "Desired filelen = " << filelen << " bytes." << endl;
    if (ftruncate64(fd, filelen) != 0)
    {
        perror("ftruncate64");
        cerr << "Couldn't ftruncate64() \"" << filename
                        << "\" to " << filelen << " bytes.\n";
        close(fd);
        fd = -1;
        unlink(filename);
        return 1;
    }

    errno = 0;

    // mmap the file...
    //
    caddr_t  the_map = mmap64(0,filelen,PROT_READ,MAP_SHARED,fd,0);

    if (the_map == MAP_FAILED)
    {
        int const  e = errno;
        perror("mmap64");
        cerr << "Couldn't mmap64 \"" << filename
                                     << "\", (errno=" << e << ")\n";
        close(fd);
        fd = -1;
        unlink(filename);
        return 1;
    }
    else
    {
        cout << "mmap64(" << filelen << " bytes) ok." << endl;
    }

    sleep(30);

    munmap(the_map, filelen);
    the_map = 0;

    close(fd);
    fd = -1;

    unlink(filename);

    return 0;

Quote:}