On Fri, Aug 07, 2015 at 10:28:49AM -0500, Christoph Lameter wrote: > On Fri, 7 Aug 2015, Kirill A. Shutemov wrote: > > > On Thu, Aug 06, 2015 at 03:45:31PM -0500, Christoph Lameter wrote: > > > On Thu, 6 Aug 2015, Hugh Dickins wrote: > > > > > > > > I know a patchset which solves this! ;) > > > > > > > > Oh, and I know a patchset which avoids these problems completely, > > > > by not using compound pages at all ;) > > > > > > Another dumb idea: Stop the insanity of splitting pages on the fly? > > > Splitting pages should work like page migration: Lock everything down and > > > ensure no one is using the page and then do it. That way the compound pages > > > and its metadata are as stable as a regular page. > > > > That's what I do in refcounting patchset. > > Looks like you make refcounting easier and avoid splitting in some cases > maybe only splitting the pmd. But the fundamental issue still remains. > Complexity is high since individual pages of a compound can be mapped and > unmapped in multiple processes. > > The compound would need to be always treated as a single order N entity > in order to really get things simplified and make code cleaner. > > Either all pages are mapped or none. Otherwise you have to manage the > a schizoprenic view of pages. Sometimes an order N size entity is > managed and sometimes a base page size page which is a fraction of the > whole. Such a view of a memory object is pretty difficult to manage. I don't see anything actionable here. Your wish list doesn't cope with reality. Compound pages are mapped with PTEs for almost ten years and I don't see why we should stop the practice. -- Kirill A. Shutemov -- 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>