On Fri, Dec 19, 2025 at 02:50:50PM +0100, Christian König wrote: > On 12/19/25 11:25, Maxime Ripard wrote: > > On Mon, Dec 15, 2025 at 03:53:22PM +0100, Christian König wrote: > >> On 12/15/25 14:59, Maxime Ripard wrote: > ... > >>>>> The shared ownership is indeed broken, but it's not more or less broken > >>>>> than, say, memfd + udmabuf, and I'm sure plenty of others. > >>>>> > >>>>> So we really improve the common case, but only make the "advanced" > >>>>> slightly more broken than it already is. > >>>>> > >>>>> Would you disagree? > >>>> > >>>> I strongly disagree. As far as I can see there is a huge chance we > >>>> break existing use cases with that. > >>> > >>> Which ones? And what about the ones that are already broken? > >> > >> Well everybody that expects that driver resources are *not* accounted to > >> memcg. > > > > Which is a thing only because these buffers have never been accounted > > for in the first place. > > Yeah, completely agree. By not accounting it for such a long time we > ended up with people depending on this behavior. > > Not nice, but that's what it is. > > > So I guess the conclusion is that we shouldn't > > even try to do memory accounting, because someone somewhere might not > > expect that one of its application would take too much RAM in the > > system? > > Well we do need some kind of solution to the problem. Either having > some setting where you say "This memcg limit is inclusive/exclusive > device driver allocated memory" or have a completely separate limit > for device driver allocated memory.
A device driver memory specific limit sounds like a good idea because it would make it easier to bridge the gap with dmem. Happy holidays, Maxime
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