On 07/11/2012 02:16 PM, Alexander Graf wrote: >> >>> yes the data structure itself seems based on the algorithm >>> and not on arch specific things. That should work. If we move that to common >>> code then s390 will use that scheme automatically for the cases were we call >>> kvm_vcpu_on_spin(). All others archs as well. >> >> ARM doesn't have an instruction for cpu_relax(), so it can't intercept >> it. Given ppc's dislike of overcommit, > > What dislike of overcommit? I understood ppc virtualization is more of the partitioning sort. Perhaps I misunderstood it. But the reliance on device assignment, the restrictions on scheduling, etc. all point to it. > >> and the way it implements cpu_relax() by adjusting hw thread priority, > > Yeah, I don't think we can intercept relaxing. ... and the lack of ability to intercept cpu_relax() ... > It's basically a nop-like instruction that gives hardware hints on its current priorities. That's what x88 PAUSE does. But we can intercept it (and not just any execution - we can restrict intercept to tight loops executed more than a specific number of times). > That said, we can always add PV code. Sure, but that's defeated by advancements like self-tuning PLE exits. It's hard to get this right. -- error compiling committee.c: too many arguments to function -- 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
