[SNIP]
Thanks for the input, Daniel! Let me think about the cases you pointed out.How many semi-unrelated buffer accounting schemes does google come up with?I just realized that vm_inser_page doesn't even work for CMA, it would
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.
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.
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.
Thanks,
Suren.