Hi TJ, On Fri, Dec 12, 2025 at 08:25:19AM +0900, T.J. Mercier wrote: > On Fri, Dec 12, 2025 at 4:31 AM Eric Chanudet <[email protected]> wrote: > > > > The system dma-buf heap lets userspace allocate buffers from the page > > allocator. However, these allocations are not accounted for in memcg, > > allowing processes to escape limits that may be configured. > > > > Pass the __GFP_ACCOUNT for our allocations to account them into memcg. > > We had a discussion just last night in the MM track at LPC about how > shared memory accounted in memcg is pretty broken. Without a way to > identify (and possibly transfer) ownership of a shared buffer, this > makes the accounting of shared memory, and zombie memcg problems > worse. :\
Are there notes or a report from that discussion anywhere? The way I see it, the dma-buf heaps *trivial* case is non-existent at the moment and that's definitely broken. Any application can bypass its cgroups limits trivially, and that's a pretty big hole in the system. 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? Maxime
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