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@kernel.org (local)
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