Messages in this thread |  | | Date | Sat, 14 Dec 2013 14:10:59 +0100 | From | Thomas Hellstrom <> | Subject | Re: [RFC] dma-buf: Implement test module |
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On 12/14/2013 02:02 PM, Rob Clark wrote: > On Sat, Dec 14, 2013 at 7:47 AM, Thomas Hellstrom <thomas@shipmail.org> wrote: >> On 12/14/2013 01:37 PM, Thierry Reding wrote: >>> On Thu, Dec 12, 2013 at 11:30:23PM +0100, Daniel Vetter wrote: >>>> On Thu, Dec 12, 2013 at 8:34 PM, Thomas Hellstrom <thellstrom@vmware.com> >>>> wrote: >>>>> On 12/12/2013 03:36 PM, Thierry Reding wrote: >>>>>> This is a simple test module that can be used to allocate, export and >>>>>> delete DMA-BUF objects. It can be used to test DMA-BUF sharing in >>>>>> systems that lack a real second driver. >>>>>> >>>>>> >>>>> Looks nice. I wonder whether this could be extended to create a >>>>> "streaming" >>>>> dma-buf from a user space mapping. That could be used as a generic way >>>>> to >>>>> implement streaming (user) buffer objects, rather than to add explicit >>>>> support for those in, for example, TTM. >>>> Atm there's no way to get gpus to unbind their dma-buf mappings, so >>>> their essentially pinned forever from first use on. >>> Shouldn't this work by simply calling the GEM_CLOSE IOCTL on the handle >>> returned by drmPrimeFDToHandle()? I mean that should drop the last >>> reference on the GEM object and cause it to be cleaned up (which should >>> include detaching the DMA-BUF). >> >> Actually, while the GEM prime implementation appears to pin an exported >> dma-buf on first attach, from the dma-buf documentation it seems sufficient >> to pin it on map or cpu access. >> >> But what I assume Daniel is referring to is that there is no way for >> exporters to tell importers to force unmap() the dma-buf, so that it can be >> unpinned? > yeah, or some way for importers to opportunistically keep around a > mapping rather than map/unmap on each use.. > > maybe we need something shrinker-ish for dmabuf?
Yes, I think that's needed for both the memory-shortage case where we want to unpin, and I guess it would desirable for iommu space management as well.
/Thomas
> > BR, > -R > >
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