Messages in this thread | | | Date | Mon, 11 Jul 2011 10:49:31 -0700 (PDT) | From | Hugh Dickins <> | Subject | Re: [PATCH 34/49] gma500: the GEM and GTT code is device independant |
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On Mon, 11 Jul 2011, Alan Cox wrote: > > Your <4GB pages won't get swapped out while they're pinned. But can > > it happen that they'd be unpinned, swapped out, swapped back in >4GB > > pages, then cause trouble for you when needed again? > > It does look that way, in which case that will eventually need fixing. At > the moment you can't put enough memory into a device using these chips > but that won't always be true I imagine.
Thanks, I won't worry about it at this moment, but we'd better not forget.
If it's easy for you to include a WARN_ON_ONCE check (perhaps on page_to_pfn(page)), that may be worth doing to remind us.
It's a bit sad to learn this requirement just after I'd completed removing the readpage copying code, and a bit strange to have shmem confined by hardware constraints; but I guess that's what we took on when we opened it up to GEM.
It will probably make sense for me to add synchronous migration when a shmem swap page is found not to match the contraints wanted by the mapping it goes into: mainly for NUMA, but covering your case too.
Hugh
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