On 2018-05-25 10:41 AM, Christoph Hellwig wrote: > On Tue, May 22, 2018 at 03:13:58PM +0200, Christian König wrote: >> Am 02.05.2018 um 18:59 schrieb Michel Dänzer: >>> On 2018-05-02 06:21 PM, Christoph Hellwig wrote: >>>> On Wed, May 02, 2018 at 04:31:09PM +0200, Michel Dänzer wrote: >>>>>> No. __GFP_NOWARN (and gfp_t flags in general) are the wrong interface >>>>>> for dma allocations and just cause problems. I actually plan to >>>>>> get rid of the gfp_t argument in dma_alloc_attrs sooner, and only >>>>>> allow either GFP_KERNEL or GFP_DMA passed in dma_alloc_coherent. >>>>> How about GFP_TRANSHUGE_LIGHT? TTM uses that to opportunistically >>>>> allocate huge pages (GFP_TRANSHUGE can result in unacceptably long >>>>> delays with memory pressure). >>>> Well, that is exactly what I don't want drivers to do - same for >>>> __GFP_COMP in some drm code. This very much assumes the page allocator >>>> is used to back dma allocations, which very often it actually isn't, and >>>> any use of magic gfp flags creates a tight coupling of consumers with a >>>> specific implementation. >>>> >>>> In general I can't think of a good reason not to actually use >>>> GFP_TRANSHUGE_LIGHT by default in the dma allocator unless >>>> DMA_ATTR_ALLOC_SINGLE_PAGES is set. Can you prepare a patch for that? >>> I'm afraid I'll have to leave that to somebody else. >> >> Coming back to this topic once more, sorry for the delay but busy as usual >> :) >> >> What exactly do you mean with "dma allocator" here? The TTM allocator using >> the dma_alloc_coherent calls? Or the swiotlb implementation of the calls? > > dma allocatr in this case: backends for dma_alloc_coherent/ > dma_alloc_attrs. Most importantly dma_direct_alloc. > > But while we're at it I can't actually see any GFP_TRANSHUGE_LIGHT > usage in TTM, just plain old GFP_TRANSHUGE. See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=da291320baec914f0bb4e65a9dccb86bd6c728f2 . -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
