Messages in this thread |  | | Date | Mon, 26 Sep 2011 19:47:24 -0300 | | From | Glauber Costa <> | | Subject | Re: [PATCH v3 2/7] socket: initial cgroup code. |
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On 09/26/2011 07:52 AM, KAMEZAWA Hiroyuki wrote: > On Sat, 24 Sep 2011 11:45:04 -0300 > Glauber Costa<glommer@parallels.com> wrote: > >> On 09/22/2011 12:09 PM, Balbir Singh wrote: >>> On Thu, Sep 22, 2011 at 11:30 AM, Greg Thelen<gthelen@google.com> wrote: >>>> On Wed, Sep 21, 2011 at 11:59 AM, Glauber Costa<glommer@parallels.com> wrote: >>>>> Right now I am working under the assumption that tasks are long lived inside >>>>> the cgroup. Migration potentially introduces some nasty locking problems in >>>>> the mem_schedule path. >>>>> >>>>> Also, unless I am missing something, the memcg already has the policy of >>>>> not carrying charges around, probably because of this very same complexity. >>>>> >>>>> True that at least it won't EBUSY you... But I think this is at least a way >>>>> to guarantee that the cgroup under our nose won't disappear in the middle of >>>>> our allocations. >>>> >>>> Here's the memcg user page behavior using the same pattern: >>>> >>>> 1. user page P is allocate by task T in memcg M1 >>>> 2. T is moved to memcg M2. The P charge is left behind still charged >>>> to M1 if memory.move_charge_at_immigrate=0; or the charge is moved to >>>> M2 if memory.move_charge_at_immigrate=1. >>>> 3. rmdir M1 will try to reclaim P (if P was left in M1). If unable to >>>> reclaim, then P is recharged to parent(M1). >>>> >>> >>> We also have some magic in page_referenced() to remove pages >>> referenced from different containers. What we do is try not to >>> penalize a cgroup if another cgroup is referencing this page and the >>> page under consideration is being reclaimed from the cgroup that >>> touched it. >>> >>> Balbir Singh >> Do you guys see it as a showstopper for this series to be merged, or can >> we just TODO it ? >> > > In my experience, 'I can't rmdir cgroup.' is always an important/difficult > problem. The users cannot know where the accouting is leaking other than > kmem.usage_in_bytes or memory.usage_in_bytes. and can't fix the issue. > > please add EXPERIMENTAL to Kconfig until this is fixed.
I am working on something here that may allow it. But I think it is independent of the rest, and I can repost the series fixing the problems raised here without it, + EXPERIMENTAL.
Btw, using EXPERIMENTAL here is a very good idea. I think that we should turn EXPERIMENTAL on even if I fix for that exists, for a least a couple of months until we see how this thing really evolves.
What do you think?
>> I can push a proposal for it, but it would be done in a separate patch >> anyway. Also, we may be in better conditions to fix this when the slab >> part is merged - since it will likely have the same problems... >> > > Yes. considering sockets which can be shared between tasks(cgroups) > you'll finally need > - owner task of socket > - account moving callback > > Or disallow task moving once accounted.
I personally think disallowing task movement once accounted is reasonable. At least for starters.
I think I can add at least that to the next proposal. Famous last words is, it should not be that hard...
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