Michel Dänzer <michel@xxxxxxxxxxx> writes: > On 2018-01-19 11:02 AM, Michel Dänzer wrote: >> On 2018-01-19 10:58 AM, Christian König wrote: >>> Am 19.01.2018 um 10:32 schrieb Michel Dänzer: >>>> On 2018-01-19 09:39 AM, Christian König wrote: >>>>> Am 19.01.2018 um 09:20 schrieb Michal Hocko: >>>>>> OK, in that case I would propose a different approach. We already >>>>>> have rss_stat. So why do not we simply add a new counter there >>>>>> MM_KERNELPAGES and consider those in oom_badness? The rule would be >>>>>> that such a memory is bound to the process life time. I guess we will >>>>>> find more users for this later. >>>>> I already tried that and the problem with that approach is that some >>>>> buffers are not created by the application which actually uses them. >>>>> >>>>> For example X/Wayland is creating and handing out render buffers to >>>>> application which want to use OpenGL. >>>>> >>>>> So the result is when you always account the application who created the >>>>> buffer the OOM killer will certainly reap X/Wayland first. And that is >>>>> exactly what we want to avoid here. >>>> FWIW, what you describe is true with DRI2, but not with DRI3 or Wayland >>>> anymore. With DRI3 and Wayland, buffers are allocated by the clients and >>>> then shared with the X / Wayland server. >>> >>> Good point, when I initially looked at that problem DRI3 wasn't widely >>> used yet. >>> >>>> Also, in all cases, the amount of memory allocated for buffers shared >>>> between DRI/Wayland clients and the server should be relatively small >>>> compared to the amount of memory allocated for buffers used only locally >>>> in the client, particularly for clients which create significant memory >>>> pressure. >>> >>> That is unfortunately only partially true. When you have a single >>> runaway application which tries to allocate everything it would indeed >>> work as you described. >>> >>> But when I tested this a few years ago with X based desktop the >>> applications which actually used most of the memory where Firefox and >>> Thunderbird. Unfortunately they never got accounted for that. >>> >>> Now, on my current Wayland based desktop it actually doesn't look much >>> better. Taking a look at radeon_gem_info/amdgpu_gem_info the majority of >>> all memory was allocated either by gnome-shell or Xwayland. >> >> My guess would be this is due to pixmaps, which allow X clients to cause >> the X server to allocate essentially unlimited amounts of memory. It's a >> separate issue, which would require a different solution than what we're >> discussing in this thread. Maybe something that would allow the X server >> to tell the kernel that some of the memory it allocates is for the >> client process. > > Of course, such a mechanism could probably be abused to incorrectly > blame other processes for one's own memory consumption... > > > I'm not sure if the pixmap issue can be solved for the OOM killer. It's > an X design issue which is fixed with Wayland. So it's probably better > to ignore it for this discussion. > > Also, I really think the issue with DRM buffers being shared between > processes isn't significant for the OOM killer compared to DRM buffers > only used in the same process that allocates them. So I suggest focusing > on the latter. Agreed. The 95% case is non-shared buffers, so just don't account for them and we'll have a solution good enough that we probably never need to handle the shared case. On the DRM side, removing buffers from the accounting once they get shared would be easy.
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