On Wed 15-08-12 12:50:55, Ying Han wrote: > On Tue, Aug 14, 2012 at 9:21 AM, Michal Hocko <mho...@suse.cz> wrote: > > On Thu 09-08-12 17:01:12, Glauber Costa wrote: > >> This patch adds the basic infrastructure for the accounting of the slab > >> caches. To control that, the following files are created: > >> > >> * memory.kmem.usage_in_bytes > >> * memory.kmem.limit_in_bytes > >> * memory.kmem.failcnt > >> * memory.kmem.max_usage_in_bytes > >> > >> They have the same meaning of their user memory counterparts. They > >> reflect the state of the "kmem" res_counter. > >> > >> The code is not enabled until a limit is set. This can be tested by the > >> flag "kmem_accounted". This means that after the patch is applied, no > >> behavioral changes exists for whoever is still using memcg to control > >> their memory usage. > >> > >> We always account to both user and kernel resource_counters. This > >> effectively means that an independent kernel limit is in place when the > >> limit is set to a lower value than the user memory. A equal or higher > >> value means that the user limit will always hit first, meaning that kmem > >> is effectively unlimited. > > > > Well, it contributes to the user limit so it is not unlimited. It just > > falls under a different limit and it tends to contribute less. This can > > be quite confusing. I am still not sure whether we should mix the two > > things together. If somebody wants to limit the kernel memory he has to > > touch the other limit anyway. Do you have a strong reason to mix the > > user and kernel counters? > > The reason to mix the two together is a compromise of the two use > cases we've heard by far. In google, we only need one limit which > limits u & k, and the reclaim kicks in when the total usage hits the > limit. > > > My impression was that kernel allocation should simply fail while user > > allocations might reclaim as well. Why should we reclaim just because of > > the kernel allocation (which is unreclaimable from hard limit reclaim > > point of view)? > > Some of kernel objects are reclaimable if we have per-memcg shrinker.
Agreed and I think we need that before this is merged as I state in other email. > > I also think that the whole thing would get much simpler if those two > > are split. Anyway if this is really a must then this should be > > documented here. > > What would be the use case you have in your end? I do not have any specific unfortunately but I would like to prevent us from closing other possible. I realize this sounds hand wavy and that is why I do not want to block this work but I think we should give it some time before this gets merged. > --Ying -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
