Messages in this thread |  | | | Date | Mon, 17 Oct 2011 18:32:30 -0500 | | Subject | Re: [PATCH 34/49] gma500: the GEM and GTT code is device independant | | From | Rob Clark <> |
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On Mon, Oct 17, 2011 at 5:34 PM, Hugh Dickins <hughd@google.com> wrote: > On Mon, 17 Oct 2011, Alan Cox wrote: >> > It feels to me like GEM is pulling shmem in an ever more alien direction: >> > these device constraints are so foreign to the nature of tmpfs; and >> > beyond my expertise, so that I'd be ever more likely to make the wrong >> > decisions (mixing swap and uncached pages? hmmm). >> >> For the most part we fixed that. You can now have a GEM object that is >> backed by a private memory object rather than having to be tmpfs. >> GMA500 uses it to attach 'stolen' memory to GEM handles, and at least >> one other pending submission uses it with a private CMA style allocator. > > Sounds good.
Well, that means we could implement our own shmem/tmpfs.. although I'm not entirely sure that I would want to.. a couple drm drivers are using private memory objects, but I think primarily for scanout buffers (which can't really be swapped out anyways). I don't think we'd want to use this for everything.
What troubles could you see for swap+uncached (or more likely, writecombine) pages?
BR, -R
>> >> The gma500 report seems an odd one - no GMA500 box has >4GB memory so how >> did the test code get a page that was unsuitable - is the test buggy ? > > This is the first I heard of some gma500 test seeing a problem with >4GB. > > In this thread we have Patrik hitting the oops in read_cache_page_gfp() > because of some changes he is preparing, but I thought he and Rob were > just thinking ahead when they raise the 4GB issue. > > Can you point us to another thread on a another list? > > Hugh >
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