On Thu, Aug 16, 2012 at 8:25 AM, Michal Hocko <mhocko@xxxxxxx> wrote: > On Wed 15-08-12 12:50:55, Ying Han wrote: >> On Tue, Aug 14, 2012 at 9:21 AM, Michal Hocko <mhocko@xxxxxxx> 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. Agreed that we don't want to rush merge anything. On the other hand, I was trying to understand your concern of the k & u+k counter. After reading your previous replies, I think I understand your concern of missing the target shrinker. I posted the patch and please take a look :) Meanwhile, can you help to clarify other concerns in your mind on having the two counters? Please ignore me if you answered the question somewhere and just give me the pointer. --Ying > >> --Ying > -- > Michal Hocko > SUSE Labs -- 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>