On Fri, Jun 05, 2009 at 02:32:51AM -0700, Paul Menage wrote: > On Fri, Jun 5, 2009 at 2:27 AM, Bharata B Rao<bharata@xxxxxxxxxxxxxxxxxx> wrote: > >> > >> Suppose 10 cgroups each want 10% of the machine's CPU. We can just > >> give each cgroup an equal share, and they're guaranteed 10% if they > >> try to use it; if they don't use it, other cgroups can get access to > >> the idle cycles. > > > > 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 al 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%. How would you be able to do that with any other mechanism? 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
