On 14/02/15 16:22, Thomas Niederprüm wrote: > Am Thu, 12 Feb 2015 16:11:21 +0100 > schrieb Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>: > >> On Sat, Feb 07, 2015 at 04:35:41PM +0100, Thomas Niederprüm wrote: >>> Am Sat, 7 Feb 2015 12:18:21 +0100 >>> schrieb Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>: >>> >>>> Hi, >>>> >>>> On Fri, Feb 06, 2015 at 11:28:10PM +0100, niederp@xxxxxxxxxxxxxxxx >>>> wrote: >>>>> From: Thomas Niederprüm <niederp@xxxxxxxxxxxxxxxx> >>>>> >>>>> It makes sense to use vmalloc to allocate the video buffer >>>>> since it has to be page aligned memory for using it with mmap. >>>> >>>> Please wrap your commit log at 80 chars. >>> >>> I'll try to do so in future, sorry for that. >>> >>>> >>>> It looks like there's numerous fbdev drivers using this >>>> (especially since you copy pasted that code, without mentionning >>>> it). >>> >>> Yes, I should have mentioned that in the commit message. As >>> implicitly indicated in the cover letter the rvmalloc() and >>> rvfree() are copy pasted from the vfb driver. Honestly, I didn't >>> give this one too much thought. It seemed a viable solution to the >>> mmap problem. For a bit more history on that, see my comment below. >>> >>>> >>>> That should be turned into an allocator so that drivers all get >>>> this right. >>>> >>>>> Also deffered io seems buggy in combination with kmalloc'ed >>>>> memory (crash on unloading the module). >>>> >>>> And maybe that's the real issue to fix. >>> >>> The problem is solved by using vmalloc ;) >> >> Yep, but why do you need to mark the reserved pages? >> >> ... > > As far as I understood mmaped memory is marked as userspace memory in > the page table and is therefore subject to swapping. The pages are > marked reserved to make clear that this memory can not be swapped and > thus lock the pages in memory. See discussions [0,1,2]. Why is it a problem if it is swapped? Only CPU uses the memory, as far as I can see. Also, isn't doing __pa() for the memory returned by vmalloc plain wrong? What was the crash about when using kmalloc? It would be good to fix defio, as I don't see why it should not work with kmalloced memory. Tomi
Attachment:
signature.asc
Description: OpenPGP digital signature
