On 09/26/2012 11:56 PM, Tejun Heo wrote: > Hello, > > On Wed, Sep 26, 2012 at 11:46:37PM +0400, Glauber Costa wrote: >> Besides not being part of cgroup core, and respecting very much both >> cgroups' and basic sanity properties, kmem is an actual feature that >> some people want, and some people don't. There is no reason to believe >> that applications that want will live in the same environment with ones >> that don't want. > > I don't know. It definitely is less crazy than .use_hierarchy but I > wouldn't say it's an inherently different thing. I mean, what does it > even mean to have u+k limit on one subtree and not on another branch? > And we worry about things like what if parent doesn't enable it but > its chlidren do. > It is inherently different. To begin with, it actually contemplates two use cases. It is not a work around. The meaning is also very well defined. The meaning of having this enabled in one subtree and not in other is: Subtree A wants to track kernel memory. Subtree B does not. It's that, and never more than that. There is no maybes and no buts, no magic knobs that makes it behave in a crazy way. If a children enables it but the parent does not, this does what every tree does: enable it from that point downwards. > This is a feature which adds complexity. If the feature is necessary > and justified, sure. If not, let's please not and let's err on the > side of conservativeness. We can always add it later but the other > direction is much harder. > I disagree. Having kmem tracking adds complexity. Having to cope with the use case where we turn it on dynamically to cope with the "user page only" use case adds complexity. But I see no significant complexity being added by having it per subtree. Really. You have the use_hierarchy fiasco in mind, and I do understand that you are raising the flag and all that. But think in terms of functionality: This thing here is a lot more similar to swap than use_hierarchy. Would you argue that memsw should be per-root ? The reason why it shouldn't: Some people want to limit memory consumption all the way to the swap, some people don't. Same with kmem. -- 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>