On Tue, Jun 16, 2015 at 03:17:13PM +0200, Jerome Marchand wrote: > On 06/03/2015 07:05 PM, Kirill A. Shutemov wrote: > > Hello everybody, > > > > Here's new revision of refcounting patchset. Please review and consider > > applying. > > > > The goal of patchset is to make refcounting on THP pages cheaper with > > simpler semantics and allow the same THP compound page to be mapped with > > PMD and PTEs. This is required to get reasonable THP-pagecache > > implementation. > > > > With the new refcounting design it's much easier to protect against > > split_huge_page(): simple reference on a page will make you the deal. > > It makes gup_fast() implementation simpler and doesn't require > > special-case in futex code to handle tail THP pages. > > > > It should improve THP utilization over the system since splitting THP in > > one process doesn't necessary lead to splitting the page in all other > > processes have the page mapped. > > > > The patchset drastically lower complexity of get_page()/put_page() > > codepaths. I encourage people look on this code before-and-after to > > justify time budget on reviewing this patchset. > > > > = Changelog = > > > > v6: > > - rebase to since-4.0; > > - optimize mapcount handling: significantely reduce overhead for most > > common cases. > > - split pages on migrate_pages(); > > - remove infrastructure for handling splitting PMDs on all architectures; > > - fix page_mapcount() for hugetlb pages; > > > > Hi Kirill, > > I ran some LTP mm tests and hugemmap tests trigger the following: > > [ 438.749457] page:ffffea0000df8000 count:2 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 > [ 438.750089] flags: 0x3ffc0000004001(locked|head) > [ 438.750089] page dumped because: VM_BUG_ON_PAGE(page_mapped(page)) Did you run with original or updated version of patch 27/36? In original post of v6 there was bug: page_mapped() always returned true. -- 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>