On Fri, Jun 05, 2009 at 02:51:18AM -0700, Paul Menage wrote: > On Fri, Jun 5, 2009 at 2:48 AM, Dhaval Giani<dhaval@xxxxxxxxxxxxxxxxxx> wrote: > >> > Now if 11th group with same shares comes in, then each group will now > >> > get 9% of CPU and that 10% guarantee breaks. > >> > >> So you're trying to guarantee 11 cgroups that they can each get 10% of > >> the CPU? That's called over-committing, and while there's nothing > >> wrong with doing that if you're confident that they'll not all need > >> their 10% at the same time, there's no way to *guarantee* them all > >> 10%. You can guarantee them all 9% and hope the extra 1% is spare for > >> those that need it (over-committing), or you can guarantee 10 of them > >> 10% and give the last one 0 shares. > >> > >> How would you propose to guarantee 11 cgroups each 10% of the CPU > >> using hard limits? > >> > > > > You cannot guarantee 10% to 11 groups on any system (unless I am missing > > something). The sum of guarantees cannot exceed 100%. > > That's exactly my point. I was trying to counter Bharata's statement, which was: > > > > Now if 11th group with same shares comes in, then each group will now > > > get 9% of CPU and that 10% guarantee breaks. > > which seemed to be implying that this was a drawback of using shares > to implement guarantees. > OK :). Glad to see I did not get it wrong. I think we are focusing on the wrong use case here. Guarantees is just a useful side-effect we get by using hard limits. I think the more important use case is where the provider wants to limit the amount of time a user gets (such as in a cloud). Maybe we should direct our attention in solving that problem? :) thanks, -- regards, Dhaval -- 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
