On Tue, May 14, 2013 at 09:24:58AM +0800, Tang Chen wrote: > Hi Mel, Benjamin, Jeff, > > On 05/13/2013 11:01 PM, Benjamin LaHaise wrote: > >On Mon, May 13, 2013 at 10:54:03AM -0400, Jeff Moyer wrote: > >>How do you propose to move the ring pages? > > > >It's the same problem as doing a TLB shootdown: flush the old pages from > >userspace's mapping, copy any existing data to the new pages, then > >repopulate the page tables. It will likely require the addition of > >address_space_operations for the mapping, but that's not too hard to do. > > > > I think we add migrate_unpin() callback to decrease page->count if > necessary, > and migrate the page to a new page, and add migrate_pin() callback to pin > the new page again. You can't just decrease the page count for this to work. The pages are pinned because aio_complete() can occur at any time and needs to have a place to write the completion events. When changing pages, aio has to take the appropriate lock when changing one page for another. > The migrate procedure will work just as before. We use callbacks to > decrease > the page->count before migration starts, and increase it when the migration > is done. > > And migrate_pin() and migrate_unpin() callbacks will be added to > struct address_space_operations. I think the existing migratepage operation in address_space_operations can be used. Does it get called when hot unplug occurs? That is: is testing with the migrate_pages syscall similar enough to the memory removal case? -ben > Is that right ? > > If so, I'll be working on it. > > Thanks. :) -- "Thought is the essence of where you are now." -- 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>