From: "Paul Menage" <menage@google.com>
To: balbir@linux.vnet.ibm.com
Cc: linux-mm@kvack.org, "Sudhir Kumar" <skumar@linux.vnet.ibm.com>,
"YAMAMOTO Takashi" <yamamoto@valinux.co.jp>,
lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org,
"David Rientjes" <rientjes@google.com>,
"Pavel Emelianov" <xemul@openvz.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [-mm][PATCH 3/4] Add rlimit controller accounting and control
Date: Thu, 8 May 2008 16:22:27 -0700 [thread overview]
Message-ID: <6599ad830805081622l1d0c3716yd0a70fc246a9cf51@mail.gmail.com> (raw)
In-Reply-To: <48231438.9030803@linux.vnet.ibm.com>
On Thu, May 8, 2008 at 7:54 AM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>
> Paul Menage wrote:
> > On Sat, May 3, 2008 at 2:38 PM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> >> +
> >> +int rlimit_cgroup_charge_as(struct mm_struct *mm, unsigned long nr_pages)
> >> +{
> >> + int ret;
> >> + struct rlimit_cgroup *rcg;
> >> +
> >> + rcu_read_lock();
> >> + rcg = rlimit_cgroup_from_task(rcu_dereference(mm->owner));
> >> + css_get(&rcg->css);
> >> + rcu_read_unlock();
> >> +
> >> + ret = res_counter_charge(&rcg->as_res, (nr_pages << PAGE_SHIFT));
> >> + css_put(&rcg->css);
> >> + return ret;
> >> +}
> >
> > You need to synchronize against mm->owner changing, or
> > mm->owner->cgroups changing. How about:
> >
>
> My mind goes blank at times, so forgive me asking, what happens if we don't use
> task_lock(). mm->owner cannot be freed, even if it changes, we get the callback
> in mm_owner_changed(). The locations from where we call _charge and _uncharge,
> we know that the mm is not going to change either.
I guess I'm concerned about a race like:
A and B are threads in cgroup G, and C is a different process
A->mm->owner == B
A: enter rlimit_cgroup_charge_as()
A: charge new page to G
C: enter attach_task(newG, B)
C: update B->cgroup to point to newG
C: call memrlimit->attach(G, newG, B)
C: charge mm->total_vm to newG
C: uncharge mm->total_vm from G
A: add new page to mm->total_vm
Maybe this can be solved very simply by just taking mm->mmap_sem in
rlimit_cgroup_move_task() and rlimit_cgroup_mm_owner_changed() ? Since
mmap_sem is (I hope) held across all operations that change
mm->total_vm
>
>> Consider the following scenario
>
> We try to move task "t1" from cgroup "A" to cgroup "B".
> Doing so, causes "B" to go over it's limit, what do we do?
> Ideally, we would like to be able to go back to cgroups and say, please fail
> attach, since that causes "B" to go over it's specified limit.
>
OK, that sounds reasonable - that's what the can_attach() callback is for.
Paul
next prev parent reply other threads:[~2008-05-08 23:22 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-03 21:37 [-mm][PATCH 0/4] Add rlimit controller to cgroups (v3) Balbir Singh
2008-05-03 21:37 ` [-mm][PATCH 1/4] Setup the rlimit controller Balbir Singh
2008-05-05 22:11 ` Andrew Morton
2008-05-06 3:40 ` Balbir Singh
2008-05-06 1:31 ` Li Zefan
2008-05-06 8:15 ` Balbir Singh
2008-05-03 21:38 ` [-mm][PATCH 2/4] Enhance cgroup mm_owner_changed callback to add task information Balbir Singh
2008-05-05 22:15 ` Andrew Morton
2008-05-06 3:43 ` Balbir Singh
2008-05-05 23:00 ` Paul Menage
2008-05-03 21:38 ` [-mm][PATCH 3/4] Add rlimit controller accounting and control Balbir Singh
2008-05-05 22:24 ` Andrew Morton
2008-05-05 22:32 ` David Rientjes
2008-05-06 5:34 ` Balbir Singh
2008-05-07 3:17 ` Paul Menage
2008-05-07 5:59 ` Pavel Emelyanov
2008-05-08 14:54 ` Balbir Singh
2008-05-08 23:22 ` Paul Menage [this message]
2008-05-07 3:29 ` Paul Menage
2008-05-08 14:35 ` Balbir Singh
2008-05-08 21:45 ` Paul Menage
2008-05-09 13:35 ` Balbir Singh
2008-05-03 21:38 ` [-mm][PATCH 4/4] Add rlimit controller documentation Balbir Singh
2008-05-05 22:35 ` Andrew Morton
2008-05-06 5:39 ` Balbir Singh
2008-05-06 5:54 ` Andrew Morton
2008-05-06 7:59 ` Balbir Singh
2008-05-04 15:24 ` [-mm][PATCH 0/4] Add rlimit controller to cgroups (v3) kamezawa.hiroyu
2008-05-05 4:21 ` Balbir Singh
2008-05-07 1:09 ` KAMEZAWA Hiroyuki
2008-05-04 15:27 ` kamezawa.hiroyu
2008-05-05 4:24 ` Balbir Singh
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