I am using the current mount options:

UUID=46fc675c-f196-4be2-bf4d-461d473de6b1 / ext4
errors=remount-ro,user_xattr 0 1

And the dmesg messages I get are:

[    2.908858] EXT4-fs (sda5): mounted filesystem with ordered data
mode. Opts: (null)
[   14.167465] EXT4-fs (sda5): re-mounted. Opts: errors=remount-ro,user_xattr
[   15.512701] EXT4-fs (sda5): re-mounted. Opts:
errors=remount-ro,user_xattr,commit=0
[   20.801609] EXT4-fs (sda5): re-mounted. Opts:
errors=remount-ro,user_xattr,commit=0

How can I give you more information?

Thanks,
  Javi

On Wed, Feb 16, 2011 at 2:12 AM, Yongqiang Yang [off-list ref] wrote:

Was ext4 mounted with dealloc?

On Mon, Feb 7, 2011 at 3:41 PM, Javi [off-list ref] wrote:

quoted

I am developing a software based DSM. In order to avoid concurrent
updates on a memory page that is being updated by the runtime I am
using a shadow mapping to perform the updates. This mappings are
created by opening a file, unlinking it and mmap-ing on the file
descriptor. Everything is working but I am experiencing heavy disk I/O
during execution on a machine with a single ext4 file system. Other
machines that use ext3 partitions don't exhibit this behavior (there
is no disk I/O at all). This machine is using the kernel version
2.6.35-25-generic.

The exact steps performed to create the mappings are:

   // Create the file
   snprintf(tmp, FILENAME_MAX, "/tmp/testXXXXXX");
   int fd = mkstemp(tmp);
   if(fd < 0) return NULL;
   unlink(tmp);

   if(ftruncate(fd, count) < 0) {
       close(fd);
       return NULL;
   }
   ...

   // Create a mapping
   addr = mmap(NULL, count, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);


Does ext4 write to mmap'ed files although they don't have a name in
the file system? Am I doing anything wrong?

Thanks,
 Javi
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--
Best Wishes
Yongqiang Yang

-- 
Javi
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