On Fri, Jul 28, 2023 at 5:18 PM Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > > On Fri, Jul 28, 2023 at 01:33:47PM +0900, Sergey Senozhatsky wrote: > > On (23/07/27 17:17), Tomasz Figa wrote: > > > On Fri, Jun 30, 2023 at 7:47 PM Hsia-Jun Li wrote: > > > > > > > > Hello All > > > > > > > > This RFC tries to address the following problems: > > > > > > > > 1. Application may request too many buffers, increasing pressure to > > > > system's memory allocator(Thinking about running Android with 8K UHD > > > > playback in a system with only 2 GiB memory available); > > > > > > Yeah, I think that's something that has to be addressed. It was also > > > mentioned recently in the review of the DELETE_BUF series. I think we > > > need some kind of accounting of the allocations to the processes, so > > > that the per-process limits of memory usage could apply. Let me add > > > +Sergey Senozhatsky who often crosses his path with kernel memory > > > management. > > > > That's an interesting topic. The usual approach would be memcg: we > > create a memory controller, set memory usage limit, then move tasks > > under that controller. The last part is problematic, as it implies > > a well-behaving user-space. I'm not aware of a simple way (or any > > way for that matter) to "automatically enforce" memcg on a process > > group. > > > > From what I can tell networking code attempts to "enforce" memcg on its > > allocations, and hence has to manually charge memcg. For instance, take > > a look at sock_reserve_memory() and corresponding mem_cgroup_charge_skmem() > > call. > > > > So I wonder if we can take a closer look at what networking does and > > do something similar in vb2. > > It's a long-standing issue that would be nice to solve indeed. I however > wonder if we should do so in vb2, or instead invest our time and efforts > in transitioning to DMA heaps and solving the memory accounting issue > there. Would we then provide some way to disable MMAP buffer support for applications? Or you're thinking more about backing MMAP allocations with DMA-buf heaps internally in the kernel? Best regards, Tomasz
