Hi, On Tue, Aug 18, 2020 at 05:04:12PM +0900, Hyesoo Yu wrote: > These patch series to introduce a new dma heap, chunk heap. > That heap is needed for special HW that requires bulk allocation of > fixed high order pages. For example, 64MB dma-buf pages are made up > to fixed order-4 pages * 1024. > > The chunk heap uses alloc_pages_bulk to allocate high order page. > https://lore.kernel.org/linux-mm/20200814173131.2803002-1-minchan@xxxxxxxxxx > > The chunk heap is registered by device tree with alignment and memory node > of contiguous memory allocator(CMA). Alignment defines chunk page size. > For example, alignment 0x1_0000 means chunk page size is 64KB. > The phandle to memory node indicates contiguous memory allocator(CMA). > If device node doesn't have cma, the registration of chunk heap fails. This reminds me of an ion heap developed at Arm several years ago: https://git.linaro.org/landing-teams/working/arm/kernel.git/tree/drivers/staging/android/ion/ion_compound_page.c Some more descriptive text here: https://github.com/ARM-software/CPA It maintains a pool of high-order pages with a worker thread to attempt compaction and allocation to keep the pool filled, with high and low watermarks to trigger freeing/allocating of chunks. It implements a shrinker to allow the system to reclaim the pool under high memory pressure. Is maintaining a pool something you considered? From the alloc_pages_bulk thread it sounds like you want to allocate 300M at a time, so I expect if you tuned the pool size to match that it could work quite well. That implementation isn't using a CMA region, but a similar approach could definitely be applied. Thanks, -Brian > > The patchset includes the following: > - export dma-heap API to register kernel module dma heap. > - add chunk heap implementation. > - document of device tree to register chunk heap > > Hyesoo Yu (3): > dma-buf: add missing EXPORT_SYMBOL_GPL() for dma heaps > dma-buf: heaps: add chunk heap to dmabuf heaps > dma-heap: Devicetree binding for chunk heap > > .../devicetree/bindings/dma-buf/chunk_heap.yaml | 46 +++++ > drivers/dma-buf/dma-heap.c | 2 + > drivers/dma-buf/heaps/Kconfig | 9 + > drivers/dma-buf/heaps/Makefile | 1 + > drivers/dma-buf/heaps/chunk_heap.c | 222 +++++++++++++++++++++ > drivers/dma-buf/heaps/heap-helpers.c | 2 + > 6 files changed, 282 insertions(+) > create mode 100644 Documentation/devicetree/bindings/dma-buf/chunk_heap.yaml > create mode 100644 drivers/dma-buf/heaps/chunk_heap.c > > -- > 2.7.4 >
