On Mon, 27 Apr 2015, Jerome Glisse wrote: > > Well lets avoid that. Access to device memory comparable to what the > > drivers do today by establishing page table mappings or a generalization > > of DAX approaches would be the most straightforward way of implementing it > > and would build based on existing functionality. Page migration currently > > does not work with driver mappings or DAX because there is no struct page > > that would allow the lockdown of the page. That may require either > > continued work on the DAX with page structs approach or new developments > > in the page migration logic comparable to the get_user_page() alternative > > of simply creating a scatter gather table to just submit a couple of > > memory ranges to the I/O subsystem thereby avoiding page structs. > > What you refuse to see is that DAX is geared toward filesystem and as such > rely on special mapping. There is a reason why dax.c is in fs/ and not mm/ > and i keep pointing out we do not want our mecanism to be perceive as fs > from userspace point of view. We want to be below the fs, at the mm level > where we could really do thing transparently no matter what kind of memory > we are talking about (anonymous, file mapped, share). Ok that is why I mentioned the device memory mappings that are currently used for this purpose. You could generalize the DAX approach (which I understand as providing rw mappings to memory outside of the memory managed by the kernel and not as a fs specific thing). We can drop the DAX name and just talk about mapping to external memory if that confuses the issue. -- 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>