On Thu, Feb 4, 2021 at 3:16 AM Christian König <christian.koenig@xxxxxxx> wrote: > > Am 03.02.21 um 22:41 schrieb Suren Baghdasaryan: > > [SNIP] > >>> How many semi-unrelated buffer accounting schemes does google come up with? > >>> > >>> We're at three with this one. > >>> > >>> And also we _cannot_ required that all dma-bufs are backed by struct > >>> page, so requiring struct page to make this work is a no-go. > >>> > >>> Second, we do not want to all get_user_pages and friends to work on > >>> dma-buf, it causes all kinds of pain. Yes on SoC where dma-buf are > >>> exclusively in system memory you can maybe get away with this, but > >>> dma-buf is supposed to work in more places than just Android SoCs. > >> I just realized that vm_inser_page doesn't even work for CMA, it would > >> upset get_user_pages pretty badly - you're trying to pin a page in > >> ZONE_MOVEABLE but you can't move it because it's rather special. > >> VM_SPECIAL is exactly meant to catch this stuff. > > Thanks for the input, Daniel! Let me think about the cases you pointed out. > > > > IMHO, the issue with PSS is the difficulty of calculating this metric > > without struct page usage. I don't think that problem becomes easier > > if we use cgroups or any other API. I wanted to enable existing PSS > > calculation mechanisms for the dmabufs known to be backed by struct > > pages (since we know how the heap allocated that memory), but sounds > > like this would lead to problems that I did not consider. > > Yeah, using struct page indeed won't work. We discussed that multiple > times now and Daniel even has a patch to mangle the struct page pointers > inside the sg_table object to prevent abuse in that direction. > > On the other hand I totally agree that we need to do something on this > side which goes beyong what cgroups provide. > > A few years ago I came up with patches to improve the OOM killer to > include resources bound to the processes through file descriptors. I > unfortunately can't find them of hand any more and I'm currently to busy > to dig them up. https://lists.freedesktop.org/archives/dri-devel/2015-September/089778.html I think there was a more recent discussion, but I can't seem to find it. Alex > > In general I think we need to make it possible that both the in kernel > OOM killer as well as userspace processes and handlers have access to > that kind of data. > > The fdinfo approach as suggested in the other thread sounds like the > easiest solution to me. > > Regards, > Christian. > > > Thanks, > > Suren. > > > > > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel
