Re: [RFC][PATCH v6 0/7] Generic page pool & deferred freeing for system dmabuf heap

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Am 05.02.21 um 09:06 schrieb John Stultz:
This series is starting to get long, so I figured I'd add a
short cover letter for context.

The point of this series is trying to add both deferred-freeing
logic as well as a page pool to the DMA-BUF system heap.

This is desired, as the combination of deferred freeing along
with the page pool allows us to offload page-zeroing out of
the allocation hot path. This was done originally with ION
and this patch series allows the DMA-BUF system heap to match
ION's system heap allocation performance in a simple
microbenchmark [1] (ION re-added to the kernel for comparision,
running on an x86 vm image):

./dmabuf-heap-bench -i 0 1 system
Testing dmabuf system vs ion heaptype 0 (flags: 0x1)
---------------------------------------------
dmabuf heap: alloc 4096 bytes 5000 times in 86572223 ns          17314 ns/call
ion heap:    alloc 4096 bytes 5000 times in 97442526 ns          19488 ns/call
dmabuf heap: alloc 1048576 bytes 5000 times in 196635057 ns      39327 ns/call
ion heap:    alloc 1048576 bytes 5000 times in 357323629 ns      71464 ns/call
dmabuf heap: alloc 8388608 bytes 5000 times in 3165445534 ns     633089 ns/call
ion heap:    alloc 8388608 bytes 5000 times in 3699591271 ns     739918 ns/call
dmabuf heap: alloc 33554432 bytes 5000 times in 13327402517 ns   2665480 ns/call
ion heap:    alloc 33554432 bytes 5000 times in 15292352796 ns   3058470 ns/call

Daniel didn't like earlier attempts to re-use the network
page-pool code to achieve this, and suggested the ttm_pool be
used instead. This required pulling the fairly tightly knit
ttm_pool logic apart, but after many failed attmempts I think
I found a workable abstraction to split out shared logic.

So this series contains a new generic drm_page_pool helper
library, converts the ttm_pool to use it, and then adds the
dmabuf deferred freeing and adds support to the dmabuf system
heap to use both deferred freeing and the new drm_page_pool.

Input would be greatly appreciated. Testing as well, as I don't
have any development hardware that utilizes the ttm pool.

We can easily do the testing and the general idea sounds solid to me.

I see three major things we need to clean up here.
1. The licensing, you are moving from BSD/MIT to GPL2.
2. Don't add any new overhead to the TTM pool, especially allocating a private object per page is a no-go.
3. What are you doing with the reclaim stuff and why?
4. Keeping the documentation would be nice to have.

Regards,
Christian.


thanks
-john

[1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fandroid.googlesource.com%2Fplatform%2Fsystem%2Fmemory%2Flibdmabufheap%2F%2B%2Frefs%2Fheads%2Fmaster%2Ftests%2Fdmabuf_heap_bench.c&data=04%7C01%7Cchristian.koenig%40amd.com%7C2dc4d6cb3ee246558b9e08d8c9acef9a%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637481091933715561%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=oMgVsrdlwS%2BqZuuatjTiWDzMU9SiUW5eRar5xwT%2BHYQ%3D&reserved=0

Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: Liam Mark <lmark@xxxxxxxxxxxxxx>
Cc: Chris Goldsworthy <cgoldswo@xxxxxxxxxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
Cc: Hridya Valsaraju <hridya@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Sandeep Patil <sspatil@xxxxxxxxxx>
Cc: Daniel Mentz <danielmentz@xxxxxxxxxx>
Cc: Ørjan Eide <orjan.eide@xxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
Cc: Simon Ser <contact@xxxxxxxxxxx>
Cc: James Jones <jajones@xxxxxxxxxx>
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx

John Stultz (7):
   drm: Add a sharable drm page-pool implementation
   drm: ttm_pool: Rename the ttm_pool_dma structure to ttm_pool_page_dat
   drm: ttm_pool: Rework ttm_pool_free_page to allow us to use it as a
     function pointer
   drm: ttm_pool: Rework ttm_pool to use drm_page_pool
   dma-buf: heaps: Add deferred-free-helper library code
   dma-buf: system_heap: Add drm pagepool support to system heap
   dma-buf: system_heap: Add deferred freeing to the system heap

  drivers/dma-buf/heaps/Kconfig                |   5 +
  drivers/dma-buf/heaps/Makefile               |   1 +
  drivers/dma-buf/heaps/deferred-free-helper.c | 145 ++++++++++
  drivers/dma-buf/heaps/deferred-free-helper.h |  55 ++++
  drivers/dma-buf/heaps/system_heap.c          |  77 ++++-
  drivers/gpu/drm/Kconfig                      |   5 +
  drivers/gpu/drm/Makefile                     |   1 +
  drivers/gpu/drm/page_pool.c                  | 220 +++++++++++++++
  drivers/gpu/drm/ttm/ttm_pool.c               | 278 ++++++-------------
  include/drm/page_pool.h                      |  54 ++++
  include/drm/ttm/ttm_pool.h                   |  23 +-
  11 files changed, 639 insertions(+), 225 deletions(-)
  create mode 100644 drivers/dma-buf/heaps/deferred-free-helper.c
  create mode 100644 drivers/dma-buf/heaps/deferred-free-helper.h
  create mode 100644 drivers/gpu/drm/page_pool.c
  create mode 100644 include/drm/page_pool.h





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