* Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> [2009-06-05 12:49:46]: > * Avi Kivity <avi@xxxxxxxxxx> [2009-06-05 07:44:27]: > > > Balbir Singh wrote: > >> On Fri, Jun 5, 2009 at 11:33 AM, Avi Kivity <avi@xxxxxxxxxx> wrote: > >> > >>> Bharata B Rao wrote: > >>> > >>>>> Another way is to place the 8 groups in a container group, and limit > >>>>> that to 80%. But that doesn't work if I want to provide guarantees to > >>>>> several groups. > >>>>> > >>>>> > >>>> Hmm why not ? Reduce the guarantee of the container group and provide > >>>> the same to additional groups ? > >>>> > >>>> > >>> This method produces suboptimal results: > >>> > >>> $ cgroup-limits 10 10 0 > >>> [50.0, 50.0, 40.0] > >>> > >>> I want to provide two 10% guaranteed groups and one best-effort group. > >>> Using the limits method, no group can now use more than 50% of the > >>> resources. However, having the first group use 90% of the resources does > >>> not violate any guarantees, but it not allowed by the solution. > >>> > >>> > >> > >> How, it works out fine in my calculation > >> > >> 50 + 40 for G2 and G3, make sure that G1 gets 10%, since others are > >> limited to 90% > >> 50 + 40 for G1 and G3, make sure that G2 gets 10%, since others are > >> limited to 90% > >> 50 + 50 for G1 and G2, make sure that G3 gets 0%, since others are > >> limited to 100% > >> > > > > It's fine in that it satisfies the guarantees, but it is deeply > > suboptimal. If I ran a cpu hog in the first group, while the other two > > were idle, it would be limited to 50% cpu. On the other hand, if it > > consumed all 100% cpu it would still satisfy the guarantees (as the > > other groups are idle). > > > > The result is that in such a situation, wall clock time would double > > even though cpu resources are available. > > But then there is no other way to make a *guarantee*, guarantees come > at a cost of idling resources, no? Can you show me any other > combination that will provide the guarantee and without idling the > system for the specified guarantees? OK, I see part of your concern, but I think we could do some optimizations during design. For example if all groups have reached their hard-limit and the system is idle, should we do start a new hard limit interval and restart, so that idleness can be removed. Would that be an acceptable design point? -- Balbir -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
