* Avi Kivity <avi@xxxxxxxxxx> wrote: > On 11/08/2009 01:36 PM, Ingo Molnar wrote: > >>Three existing callbacks are: kmemcheck, mmiotrace, notifier. Two > >>of them kmemcheck, mmiotrace are enabled only for debugging, should > >>not be performance concern. And notifier call sites (two of them) > >>are deliberately, as explained by comment, not at the function entry, > >>so can't be unified with others. (And kmemcheck also has two different > >>call site BTW) > > > > We want mmiotrace to be generic distro capable so the overhead when > > the hook is not used is of concern. > > Maybe we should generalize paravirt-ops patching in case if (x) f() is > deemed too expensive. Yes, that's a nice idea. We have quite a number of 'conditional callbacks' in various critical paths that could be made lighter via such a technique. It would also free new callbacks from the 'it increases overhead even if unused' criticism and made it easier to add them. Ingo -- 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
