On 08/15/2012 04:39 PM, Michal Hocko wrote: > On Wed 15-08-12 13:33:55, Glauber Costa wrote: > [...] >>> 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? >> >> This is funny, because the first opposition I found to this work was >> "Why would anyone want to limit it separately?" =p >> >> It seems that a quite common use case is to have a container with a >> unified view of "memory" that it can use the way he likes, be it with >> kernel memory, or user memory. I believe those people would be happy to >> just silently account kernel memory to user memory, or at the most have >> a switch to enable it. >> >> What gets clear from this back and forth, is that there are people >> interested in both use cases. > > I am still not 100% sure myself. It is just clear that the reclaim would > need some work in order to do accounting like this. > Note: Besides what I've already said, right *now* in this series we are accounting just stack. So reclaimable vs not-reclaimable doesn't even get to play. It is used while the tasks are running, it gets freed after the tasks exited. I do agree we need to look to the whole picture, and reclaiming will be hard to get right. This is actually why we're addressing them separately: because they are a hard problem on their own, and the current status of accounting already solve real life problems for many, though not for all. >>> 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)? >> >> That is not what the kernel does, in general. We assume that if he wants >> that memory and we can serve it, we should. Also, not all kernel memory >> is unreclaimable. We can shrink the slabs, for instance. Ying Han >> claims she has patches for that already... > > Are those patches somewhere around? > Ying Han ? > [...] >>> 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 ? -- 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>