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Subject[PATCH v9 0/5] Generic page pool & deferred freeing for system dmabuf hea
After an unfortunately long pause (covid work-schedule burnout),
I wanted to revive and resubmit this series.

As before, the point of this series is trying to add both a page
pool as well as deferred-freeingto the DMA-BUF system heap to
improve allocation performance (so that it can match or beat the
old ION system heaps performance).

The combination of the page pool along with deferred freeing
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

./dmabuf-heap-bench -i 0 1 system
Testing dmabuf system vs ion heaptype 0 (flags: 0x1)
dmabuf heap: alloc 4096 bytes 5000 times in 79314244 ns 15862 ns/call
ion heap: alloc 4096 bytes 5000 times in 107390769 ns 21478 ns/call
dmabuf heap: alloc 1048576 bytes 5000 times in 259083419 ns 51816 ns/call
ion heap: alloc 1048576 bytes 5000 times in 340497344 ns 68099 ns/call
dmabuf heap: alloc 8388608 bytes 5000 times in 2603105563 ns 520621 ns/call
ion heap: alloc 8388608 bytes 5000 times in 3613592860 ns 722718 ns/call
dmabuf heap: alloc 33554432 bytes 5000 times in 12212492979 ns 2442498 ns/call
ion heap: alloc 33554432 bytes 5000 times in 14584157792 ns 2916831 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, so this series pulls the page pool functionality
out of the ttm_pool logic and creates a generic page pool
that can be shared.

New in v9:
* Tried to address Christian König's feedback on the page pool
changes (Kerneldoc, static functions, locking issues, duplicative
order tracking)
* Fix up Kconfig dependency issue as Reported-by:
kernel test robot <>
* Fix compiler warning Reported-by:
kernel test robot <>

I know Christian had some less specific feedback on the deferred free
work that I'd like to revisit, but I wanted to restart the discussion
with this new series, rather then trying to dregdge up and reply to
a ~4mo old thread.

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



Cc: Daniel Vetter <>
Cc: Christian Koenig <>
Cc: Sumit Semwal <>
Cc: Liam Mark <>
Cc: Chris Goldsworthy <>
Cc: Laura Abbott <>
Cc: Brian Starkey <>
Cc: Hridya Valsaraju <>
Cc: Suren Baghdasaryan <>
Cc: Sandeep Patil <>
Cc: Daniel Mentz <>
Cc: Ørjan Eide <>
Cc: Robin Murphy <>
Cc: Ezequiel Garcia <>
Cc: Simon Ser <>
Cc: James Jones <>

John Stultz (5):
drm: Add a sharable drm page-pool implementation
drm: ttm_pool: Rework ttm_pool to use drm_page_pool
dma-buf: system_heap: Add drm pagepool support to system heap
dma-buf: heaps: Add deferred-free-helper library code
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 | 138 +++++++++
drivers/dma-buf/heaps/deferred-free-helper.h | 55 ++++
drivers/dma-buf/heaps/system_heap.c | 46 ++-
drivers/gpu/drm/Kconfig | 4 +
drivers/gpu/drm/Makefile | 2 +
drivers/gpu/drm/page_pool.c | 297 +++++++++++++++++++
drivers/gpu/drm/ttm/ttm_pool.c | 167 ++---------
include/drm/page_pool.h | 68 +++++
include/drm/ttm/ttm_pool.h | 14 +-
11 files changed, 643 insertions(+), 154 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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