On 30.01.2018 11:48, Michel Dänzer wrote: > On 2018-01-30 11:42 AM, Daniel Vetter wrote: >> On Tue, Jan 30, 2018 at 10:43:10AM +0100, Michel Dänzer wrote: >>> On 2018-01-30 10:31 AM, Daniel Vetter wrote: >>> >>>> I guess a good first order approximation would be if we simply charge any >>>> newly allocated buffers to the process that created them, but that means >>>> hanging onto lots of mm_struct pointers since we want to make sure we then >>>> release those pages to the right mm again (since the process that drops >>>> the last ref might be a totally different one, depending upon how the >>>> buffers or DRM fd have been shared). >>>> >>>> Would it be ok to hang onto potentially arbitrary mmget references >>>> essentially forever? If that's ok I think we can do your process based >>>> account (minus a few minor inaccuracies for shared stuff perhaps, but no >>>> one cares about that). >>> >>> Honestly, I think you and Christian are overthinking this. Let's try >>> charging the memory to every process which shares a buffer, and go from >>> there. >> >> I'm not concerned about wrongly accounting shared buffers (they don't >> matter), but imbalanced accounting. I.e. allocate a buffer in the client, >> share it, but then the compositor drops the last reference. > > I don't think the order matters. The memory is "uncharged" in each > process when it drops its reference. Daniel made a fair point about passing DRM fds between processes, though. It's not a problem with how the fds are currently used, but somebody could do the following: 1. Create a DRM fd in process A, allocate lots of buffers. 2. Pass the fd to process B via some IPC mechanism. 3. Exit process A. There needs to be some assurance that the BOs are accounted as belonging to process B in the end. Cheers, Nicolai -- Lerne, wie die Welt wirklich ist, Aber vergiss niemals, wie sie sein sollte.
