On 08/15/2012 05:26 PM, Michal Hocko wrote: > On Wed 15-08-12 17:04:31, Glauber Costa wrote: >> On 08/15/2012 05:02 PM, Michal Hocko wrote: >>> On Wed 15-08-12 16:53:40, Glauber Costa wrote: >>> [...] >>>>>>> This doesn't check for the hierachy so kmem_accounted might not be in >>>>>>> sync with it's parents. mem_cgroup_create (below) needs to copy >>>>>>> kmem_accounted down from the parent and the above needs to check if this >>>>>>> is a similar dance like mem_cgroup_oom_control_write. >>>>>>> >>>>>> >>>>>> I don't see why we have to. >>>>>> >>>>>> I believe in a A/B/C hierarchy, C should be perfectly able to set a >>>>>> different limit than its parents. Note that this is not a boolean. >>>>> >>>>> Ohh, I wasn't clear enough. I am not against setting the _limit_ I just >>>>> meant that the kmem_accounted should be consistent within the hierarchy. >>>>> >>>> >>>> If a parent of yours is accounted, you get accounted as well. This is >>>> not the state in this patch, but gets added later. Isn't this enough ? >>> >>> But if the parent is not accounted, you can set the children to be >>> accounted, right? Or maybe this is changed later in the series? I didn't >>> get to the end yet. >>> >> >> Yes, you can. Do you see any problem with that? > > Well, if a child contributes with the kmem charges upwards the hierachy > then a parent can have kmem.usage > 0 with disabled accounting. > I am not saying this is a no-go but it definitely is confusing and I do > not see any good reason for it. I've considered it as an overlook rather > than a deliberate design decision. > No, it is not an overlook. It is theoretically possible to skip accounting on non-limited parents, but how expensive is that? This is, indeed, confusing. Of course I can be biased, but the way I see it, once you have hierarchy, you account everything your child accounts. I really don't see what is the concern here. -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>