* H. Peter Anvin <hpa@xxxxxxxxx> wrote: > On 11/08/2009 04:51 AM, Ingo Molnar wrote: > > > > * 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. > > There are a number of other things were we permanently bind to a > single instance of something, too. Optimizing those away would be > nice. Consider memcpy(), where we may want to have different > implementations for different processors. yeah. 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
