Messages in this thread | | | Date | Wed, 16 Jun 2010 13:51:09 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] use find_lock_task_mm in memory cgroups oom v2 |
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On Wed, 16 Jun 2010 10:12:20 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> On Wed, Jun 16, 2010 at 5:33 AM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@jp.fujitsu.com> wrote: > > On Tue, 15 Jun 2010 18:59:25 +0900 > > Minchan Kim <minchan.kim@gmail.com> wrote: > > > >> > -/* > >> > +/** > >> > + * find_lock_task_mm - Checking a process which a task belongs to has valid mm > >> > + * and return a locked task which has a valid pointer to mm. > >> > + * > >> > >> This comment should have been another patch. > >> BTW, below comment uses "subthread" word. > >> Personally it's easy to understand function's goal to me. :) > >> > >> How about following as? > >> Checking a process which has any subthread with vaild mm > >> .... > >> > > Sure. thank you. v2 is here. I removed unnecessary parts. > > > > == > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > > > When the OOM killer scans task, it check a task is under memcg or > > not when it's called via memcg's context. > > > > But, as Oleg pointed out, a thread group leader may have NULL ->mm > > and task_in_mem_cgroup() may do wrong decision. We have to use > > find_lock_task_mm() in memcg as generic OOM-Killer does. > > > > Changelog: > > - removed unnecessary changes in comments. > > > > mm->owner solves the same problem, but unfortunately we have task > based selection in OOM killer, so we need this patch. It is quite > ironic that we find the mm from the task and then eventually the task > back from mm->owner and then the mem cgroup. If we already know the mm > from oom_kill.c, I think we can change the function to work off of > that. mm->owner->cgroup..no? >
There is no function as for_each_mm(). There is only for_each_process().
And, generally, there is no way to get a task via mm_struct. To send signal etc. we need task. (mm_owner is an option but not always configured and there will be complicated problem as vfork() etc.)
I think oom_kill.c has to depend on thread, not mm, unfortunately.
Thanks, -Kame
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