Messages in this thread | | | Date | Thu, 15 Jan 2009 13:54:05 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete |
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On Thu, 15 Jan 2009 10:15:57 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-15 13:41:14]: > > > On Thu, 15 Jan 2009 09:47:50 +0530 > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-15 12:24:16]: > > > > > > But I don't like -EBUSY ;) > > > > > > > > When rmdir() returns -EBUSY even if there are no (visible) children and tasks, > > > > our customer will take kdump and send it to me "please explain this kernel bug" > > > > > > > > I'm sure it will happen ;) > > > > > > > > > > OK, but memory.stat can show why the group is busy and with > > > move_to_parent() such issues should not occur right? I'll relook at > > > the code. Thanks for your input. > > > > > > > There was a design choice at swap_cgroup. > > > > At rmdir, there may be used swap entry in memcg. (mem->memsw.usage can be > 0) > > 1. update all records in swap cgroup > > 2. just ignore account from swap, we can treat then at swap-in. > > > > I implemented "2" by refcnt. > > > > To do "1", we have to scan all used swap_cgroup but I don't want to scan all > > swap_cgroup entry at rmdir. It's heavy job. > > (*) To reduce memory usage by swap_cgroup, swap_cgroup just have a pointer to memcg > > (**) I implemented swap_cgroup as statically allocated array because I don't want > > any dynamic memory allocation at swap-out and want to avoid unnecessary memory > > usage. > > Fair enough, but I don't like that we don't have any checks for > > If parent still has children, parent should not go away. The > problem that Daisuke-San is seeing. > The parent has "no children" in cgroup layer. It just has children in "memory subsys" layer.
It's better to add mem_cgroup_get()/put agaisnt the parent at create()/destroy(). I'm now preparing a patch.
-Kame
> -- > Balbir >
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