Messages in this thread | | | Date | Wed, 25 Apr 2012 11:43:28 -0300 | From | Glauber Costa <> | Subject | Re: [PATCH 17/23] kmem controller charge/uncharge infrastructure |
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On 04/24/2012 07:54 PM, David Rientjes wrote: > On Tue, 24 Apr 2012, Glauber Costa wrote: > >>> Yes, for user memory, I see charging to p->mm->owner as allowing that >>> process to eventually move and be charged to a different memcg and there's >>> no way to do proper accounting if the charge is split amongst different >>> memcgs because of thread membership to a set of memcgs. This is >>> consistent with charges for shared memory being moved when a thread >>> mapping it moves to a new memcg, as well. >> >> But that's the problem. >> >> When we are dealing with kernel memory, we are allocating a whole slab page. >> It is essentially impossible to track, given a page, which task allocated >> which object. >> > > Right, so you have to make the distinction that slab charges cannot be > migrated by memory.move_charge_at_immigrate (and it's not even specified > to do anything beyond user pages in Documentation/cgroups/memory.txt),
Never intended to.
> but > it would be consistent to charge the same memcg for a process's slab > allocations as the process's user allocations. > > My response was why we shouldn't be charging user pages to > mem_cgroup_from_task(current) rather than > mem_cgroup_from_task(current->mm->owner) which is what is currently > implemented.
Ah, all right. Well, for user memory I agree with you. My point was exactly that user memory can always be pinpointed to a specific address space, while kernel memory can't.
> > If that can't be changed so that we can still migrate user memory amongst > memcgs for memory.move_charge_at_immigrate, then it seems consistent to > have all allocations done by a task to be charged to the same memcg. > Hence, I suggested current->mm->owner for slab charging as well.
All right. This can be done. Although I don't see this as a must for slab as already explained, I certainly don't oppose doing so as well.
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