On Sat, 14 Apr 2012, Haojian Zhuang wrote: > On Sat, Apr 14, 2012 at 2:27 AM, Christoph Lameter <cl@xxxxxxxxx> wrote: > > On Fri, 13 Apr 2012, Haojian Zhuang wrote: > > > >> I have one question on memory migration. As we know, malloc() from > >> user app will allocate MIGRATE_MOVABLE pages. But if we want to use > >> this memory as DMA usage, we can't accept MIGRATE_MOVABLE type. Could > >> we change its behavior before DMA working? > > > > MIGRATE_MOVABLE works fine for DMA. If you keep a reference from a device > > driver to user pages then you will have to increase the page refcount > > which will in turn pin the page and make it non movable for as long as you > > keep the refcount. > > Hi Christoph, > > Thanks for your illustration. But it's a little abstract. Could you > give me a simple example > or show me the code? Run get_user_pages() on the memory you are interest in pinning. See how other drivers do that by looking up other use cases. F.e. ib_umem_get() does a similar thing. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>