On Thu 21-07-16 22:13:55, zhong jiang wrote: > On 2016/7/21 22:01, Michal Hocko wrote: > > On Thu 21-07-16 21:58:23, zhong jiang wrote: > >> On 2016/7/21 21:40, Michal Hocko wrote: > >>> On Thu 21-07-16 21:25:38, zhong jiang wrote: > >>>> On 2016/7/21 20:55, Michal Hocko wrote: > >>> [...] > >>>>> OK, now I understand what you mean. So you mean that a different process > >>>>> initiates the migration while this path copies to pte. That is certainly > >>>>> possible but I still fail to see what is the problem about that. > >>>>> huge_pte_alloc will return the identical pte whether it is regular or > >>>>> migration one. So what exactly is the problem? > >>>>> > >>>> copy_hugetlb_page_range obtain the shared dst_pte, it may be not equal > >>>> to the src_pte. The dst_pte can come from other process sharing the > >>>> mapping. > >>> So you mean that the parent doesn't have the shared pte while the child > >>> would get one? > >>> > >> no, parent must have the shared pte because the the child copy the > >> parent. but parent is not the only source pte we can get. when we > >> scan the maping->i_mmap, firstly ,it can obtain a shared pte from > >> other process. but I am not sure. > > But then all the shared ptes should be identical, no? Or am I missing > > something? > all the shared ptes should be identical, but there is a possibility that new process > want to share the pte from other process , other than the parent, For the first time > the process is about to share pte with it. is it possiblity? I do not see how. They are opperating on the same mapping so I really do not see how different process makes any difference. -- Michal Hocko SUSE Labs -- 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>