On Thu, Jan 20, 2011 at 09:56:27AM -0800, Jeremy Fitzhardinge wrote: > > The key here is not to > > sleep when waiting for locks (as implemented by current patch-series, which can > > put other VMs at an advantage by giving them more time than they are entitled > > to) > > Why? If a VCPU can't make progress because its waiting for some > resource, then why not schedule something else instead? In the process, "something else" can get more share of cpu resource than its entitled to and that's where I was bit concerned. I guess one could employ hard-limits to cap "something else's" bandwidth where it is of real concern (like clouds). > Presumably when > the VCPU does become runnable, the scheduler will credit its previous > blocked state and let it run in preference to something else. which may not be sufficient for it to gain back bandwidth lost while blocked (speaking of mainline scheduler atleast). > > Is there a way we can dynamically expand the size of lock only upon contention > > to include additional information like owning vcpu? Have the lock point to a > > per-cpu area upon contention where additional details can be stored perhaps? > > As soon as you add a pointer to the lock, you're increasing its size. I didn't really mean to expand size statically. Rather have some bits of the lock word store pointer to a per-cpu area when there is contention (somewhat similar to how bits of rt_mutex.owner are used). I haven't thought thr' this in detail to see if that is possible though. - vatsa -- 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
