[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] A question no one can answer
On Thu, 14 Feb 2008 22:24:18 -0500 "Robert Stober" <rstober@xxxxxxxxxxxx> wrote: > Weiming, > > I agree that it is very hard, and that no one has done it. But > nevertheless I suggest the following question to the Xen developers: > > Given the fact that memory bandwidth is shared amongst multiple cores on > a single die, assume that one VM is running on each core. What is to > stop one VM from saturating the memory bus, causing reduced performance > of all the other VMs? This is the general multi-core problem, not > specific to Xen. But it affects Xen greatly. What use is it to allocate > memory to a VM if it can't use the memory because a process of another > VM has saturated the memory bus? Its perfectly doable on modern x86 - you use the profiling registers and set them up so you get a threshold interrupt when too much main memory traffic is counted (which you use to reschedule punishing the memory user). There are research papers on it from quite a long time back but afaik nobody ever implemented it in production although its not too hard to do so might be an interesting project. Alan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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