On Wed, Jan 24, 2018 at 01:11:09PM +0100, Christian König wrote: > Am 24.01.2018 um 12:50 schrieb Michal Hocko: > > On Wed 24-01-18 12:23:10, Michel Dänzer wrote: > > > On 2018-01-24 12:01 PM, Michal Hocko wrote: > > > > On Wed 24-01-18 11:27:15, Michel Dänzer wrote: > > [...] > > > > > 2. If the OOM killer kills a process which is sharing BOs with another > > > > > process, this should result in the other process dropping its references > > > > > to the BOs as well, at which point the memory is released. > > > > OK. How exactly are those BOs mapped to the userspace? > > > I'm not sure what you're asking. Userspace mostly uses a GEM handle to > > > refer to a BO. There can also be userspace CPU mappings of the BO's > > > memory, but userspace doesn't need CPU mappings for all BOs and only > > > creates them as needed. > > OK, I guess you have to bear with me some more. This whole stack is a > > complete uknonwn. I am mostly after finding a boundary where you can > > charge the allocated memory to the process so that the oom killer can > > consider it. Is there anything like that? Except for the proposed file > > handle hack? > > Not that I knew of. > > As I said before we need some kind of callback that a process now starts to > use a file descriptor, but without anything from that file descriptor mapped > into the address space. For more context: With DRI3 and wayland the compositor opens the DRM fd and then passes it to the client, which then starts allocating stuff. That makes book-keeping rather annoying. 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). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
