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

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Message-ID: <adatyz1d17q.fsf@cisco.com>
Date:	Thu, 17 Sep 2009 08:45:29 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>,
	general@...ts.openfabrics.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: [ofa-general] Re: [GIT PULL] please pull ummunotify


 > > > 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.

 - R.
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