Re: [ofa-general] Re: [GIT PULL] please pull ummunotify

Pavel Machek
2009-09-29T17:13:32Z

On Thu 2009-09-17 08:45:29, Roland Dreier wrote:
>
> > > > Hmm, or are you saying you can only get 1 event per registered range and
> > > > allocate the thing on registration? That'd need some registration limit
> > > > to avoid DoS scenarios.
> > >
> > > Yes, that's what I do. You're right, I should add a limit... although
> > > their are lots of ways for userspace to consume arbitrary amounts of
> > > kernel resources already.
> >
> > I'd be good to work at reducing that number, not adding to it ;-)
>
> Yes, definitely. I'll add a quick ummunotify module parameter that
> limits the number of registrations per process.
>
> > But yeah, I currently don't see a very nice match to perf counters.
>
> OK. It would be nice to tie into something more general, but I think I
> agree -- perf counters are missing the filtering and the "no lost
> events" that ummunotify does have. And I'm not sure it's worth messing
> up the perf counters design just to jam one more not totally related
> thing in.

I believe that extending perf counters to do what you want is better
than adding one more, very strange, user<->kernel interface.
Pavel
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