On Tue, Apr 23, 2013 at 4:40 AM, Michal Hocko <mhocko@xxxxxxx> wrote: > On Tue 23-04-13 14:17:22, Glauber Costa wrote: >> On 04/23/2013 01:58 PM, Michel Lespinasse wrote: >> > On Mon, Apr 22, 2013 at 8:54 AM, Michal Hocko <mhocko@xxxxxxx> wrote: >> >> On Mon 22-04-13 08:46:20, Tejun Heo wrote: >> >>> Oh, if so, I'm happy. Sorry about being brash on the thread; however, >> >>> please talk with google memcg people. They have very different >> >>> interpretation of what "softlimit" is and are using it according to >> >>> that interpretation. If it *is* an actual soft limit, there is no >> >>> inherent isolation coming from it and that should be clear to >> >>> everyone. >> >> >> >> We have discussed that for a long time. I will not speak for Greg & Ying >> >> but from my POV we have agreed that the current implementation will work >> >> for them with some (minor) changes in their layout. >> >> As I have said already with a careful configuration (e.i. setting the >> >> soft limit only where it matters - where it protects an important >> >> memory which is usually in the leaf nodes) >> > >> > I don't like your argument that soft limits work if you only set them >> > on leaves. To me this is just a fancy way of saying that hierarchical >> > soft limits don't work. >> > >> > Also it is somewhat problematic to assume that important memory can >> > easily be placed in leaves. This is difficult to ensure when >> > subcontainer destruction, for example, moves the memory back into the >> > parent. >> > >> >> Michal, >> >> For the most part, I am siding with you in this discussion. >> But with this only-in-leaves thing, I am forced to flip (at least for this). >> >> You are right when you say that in a configuration with A being parent >> of B and C, A being over its hard limit will affect reclaim in B and C, >> and soft limits should work the same. >> >> However, "will affect reclaim" is a big vague. More specifically, if the >> sum of B and C's hard limit is smaller or equal A's hard limit, the only >> way of either B or C to trigger A's hard limit is for them, themselves, >> to go over their hard limit. > > Which is an expectation that you cannot guarantee. You can have B+C>A. > >> *This* is the case you you are breaking when you try to establish a >> comparison between soft and hard limits - which is, per se, sane. >> >> Translating this to the soft limit speech, if the sum of B and C's soft >> limit is smaller or equal A's soft limit, and one of them is over the >> soft limit, that one should be reclaimed. The other should be left alone. > > And yet again. Nothing will prevent you from setting B+C>A. Sure if you > configure your hierarchy sanely then everything will just work. Let's all stop using words such as "sanely" and "work" since we don't see to agree on how they apply here :) The issue I see is that even when people configure soft limits B+C < A, your current proposal still doesn't "leave the other alone" as Glauber and I think we should. -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
