On Fri, Jan 15, 2016 at 11:41:50AM -0800, Darrick J. Wong wrote: > On Fri, Jan 08, 2016 at 02:49:44PM -0500, Matthew Wilcox wrote: > > From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx> > > > > Andrew, I think this is ready for a spin in -mm. > > > > v3: Rebased against current mmtom > > v2: Reduced churn in filesystems by switching to ->huge_fault interface > > Addressed concerns from Kirill > > > > We have customer demand to use 1GB pages to map DAX files. Unlike the 2MB > > page support, the Linux MM does not currently support PUD pages, so I have > > attempted to add support for the necessary pieces for DAX huge PUD pages. > > > > Filesystems still need work to allocate 1GB pages. With ext4, I can > > only get 16MB of contiguous space, although it is aligned. With XFS, > > I can get 80MB less than 1GB, and it's not aligned. The XFS problem > > may be due to the small amount of RAM in my test machine. > > "It's not aligned"... I don't know the details of what you're trying to do, but > are you trying to create a file where each GB of logical address space maps to > a contiguous GB of physical space, and both logical and physical offsets align > to a 1GB boundary? > > If the XFS is formatted with stripe unit/width of 1G, an extent size hint of 1G > is put on the file, and the whole file is allocated in 1G chunks, I think > you're supposed to be able to make the above happen: If you really, really want to guarantee 1GB aligned extents for file data on XFS, use the realtime device with a 1GB extent size..... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>