On Mon, 26 Sep 2011 19:47:24 -0300 Glauber Costa <glommer@xxxxxxxxxxxxx> wrote: > On 09/26/2011 07:52 AM, KAMEZAWA Hiroyuki wrote: > > On Sat, 24 Sep 2011 11:45:04 -0300 > > Glauber Costa<glommer@xxxxxxxxxxxxx> wrote: > > > >> On 09/22/2011 12:09 PM, Balbir Singh wrote: > >>> On Thu, Sep 22, 2011 at 11:30 AM, Greg Thelen<gthelen@xxxxxxxxxx> wrote: > >>>> On Wed, Sep 21, 2011 at 11:59 AM, Glauber Costa<glommer@xxxxxxxxxxxxx> 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? > Yes, I think so. IIRC, SWAP accounting was EXPERIMENTAL for a year. > >> 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. > Hmm. I'm ok with that...but I'm not very sure how that will be trouble. So, please make it debuggable why task cannot be moved. 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>