Re: [PATCH 02/11] Add "handle page fault" PV helper.

[Ingo Molnar]

* 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 linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/