(2012/10/17 22:30), Michal Hocko wrote: > Hi, > memcg is the only controller which might fail in its pre_destroy > callback which makes the cgroup core more complicated for no good > reason. This is an attempt to change this unfortunate state. > > I am sending this a RFC because I would like to hear back whether the > approach is correct. I thought that the changes would be more invasive > but it seems that the current code was mostly prepared for this and it > needs just some small tweaks (so I might be missing something important > here). > > The first two patches are just clean ups. They could be merged even > without the rest. > > The real change, although the code is not changed that much, is the 3rd > patch. It changes the way how we handle mem_cgroup_move_parent failures. > We have to realize that all those failures are *temporal*. Because we > are either racing with the page removal or the page is temporarily off > the LRU because of migration resp. global reclaim. As a result we do > not fail mem_cgroup_force_empty_list if the page cannot be moved to the > parent and rather retry until the LRU is empty. > > The 4th patch is for cgroup core. I have moved cgroup_call_pre_destroy > inside the cgroup_lock which is not very nice because the callbacks > can take some time. Maybe we can move this call at the very end of the > function? > All I need for memcg is that cgroup_call_pre_destroy has been called and > that no new cgroups can be attached to the group. The cgroup_lock is > necessary for the later condition but if we move after CGRP_REMOVED flag > is set then we are safe as well. > > The last two patches are trivial follow ups for the cgroups core change > because now we know that nobody will interfere with us so we can drop > those empty && no child condition. > > Comments, thoughts? > > Michal Hocko (6): > memcg: split mem_cgroup_force_empty into reclaiming and reparenting parts > memcg: root_cgroup cannot reach mem_cgroup_move_parent > memcg: Simplify mem_cgroup_force_empty_list error handling > cgroups: forbid pre_destroy callback to fail > memcg: make mem_cgroup_reparent_charges non failing > hugetlb: do not fail in hugetlb_cgroup_pre_destroy > > Cumulative diffstat: > kernel/cgroup.c | 30 ++++--------- > mm/hugetlb_cgroup.c | 11 ++--- > mm/memcontrol.c | 124 +++++++++++++++++++++++++++------------------------ > 3 files changed, 78 insertions(+), 87 deletions(-) Thank you very much ! The whole patch seems good to me and I like this approach. Thanks, -Kame -- 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>