On 2016/7/21 22:27, Michal Hocko wrote: > 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. > ok , In a words . the new process get the shared pte, The shared pte not come from the parent process. so , src_pte is not equal to dst_pte. because src_pte come from the parent, while dst_pte come from other process. obviously, it is not same. -- 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>