Forwarding off-list email On Fri 29-03-13 18:24:01, Aneesh Kumar K.V wrote: > Michal Hocko <mhocko@xxxxxxx> writes: > > > On Fri 29-03-13 10:56:00, Aneesh Kumar K.V wrote: > >> Michal Hocko <mhocko@xxxxxxx> writes: > > [...] > >> > Little bit offtopic: > >> > Btw. hugetlb migration breaks to charging even before this patchset > >> > AFAICS. The above put_page should remove the last reference and then it > >> > will uncharge it but I do not see anything that would charge a new page. > >> > This is all because regula LRU pages are uncharged when they are > >> > unmapped. But this a different story not related to this series. > >> > >> > >> But when we call that put_page, we would have alreayd move the cgroup > >> information to the new page. We have > >> > >> h_cg = hugetlb_cgroup_from_page(oldhpage); > >> set_hugetlb_cgroup(oldhpage, NULL); > >> > >> /* move the h_cg details to new cgroup */ > >> set_hugetlb_cgroup(newhpage, h_cg); > >> > >> > >> in hugetlb_cgroup_migrate > > > > Yes but the res counter charge would be missing for the newpage after > > put_page > > > > Moving this to private as i didn't get what you meant here. > > We unchage hugepage via > > __put_compound_page -> free_huge_page -> hugetlb_cgroup_uncharge_page > > That does > > h_cg = hugetlb_cgroup_from_page(page); > if (unlikely(!h_cg)) > return; > > During migrate we do > set_hugetlb_cgroup(oldhpage, NULL); > > /* move the h_cg details to new cgroup */ > set_hugetlb_cgroup(newhpage, h_cg); > > So when we do a put_page(oldhpage), we won't be finding any cgroup > attached to it and hence won't be updating the cgroup res counter value. > > So not sure what you mean by res counter change would be missing for the > newpage after put_page. I may be missing something here. Can you explain > ? Dang! You are right of course. I have missed the !h_cg check in hugetlb_cgroup_uncharge_page. Sorry about the confusion. I am so distracted by many issues these days... Thanks! -- 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>