On Wed, Nov 02, 2005 at 05:28:35PM -0600, Rob Landley wrote:

With fragmentation reduction and prezeroing, UML suddenly gains the option of 
calling madvise(DONT_NEED) on sufficiently large blocks as A) a fast way of 
prezeroing, B) a way of giving memory back to the host OS when it's not in 
use.

DONT_NEED is insufficient.  It doesn't discard the data in dirty
file-backed pages.

Badari Pulavarty has a test patch (google for madvise(MADV_REMOVE))
which does do the trick, and I have a UML patch which adds memory
hotplug.  This combination does free memory back to the host.

				Jeff

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>