[RFC][PATCH 0/6] dma-buf: Performance improvements for system heap

[John Stultz]

Hey All,
  So this patch series contains a series of performance
optimizations to the dma-buf system heap.

Unfortunately, in working these up, I realized the heap-helpers
infrastructure we tried to add to miniimize code duplication is
not as generic as we intended. For some heaps it makes sense to
deal with page lists, for other heaps it makes more sense to
track things with sgtables.

So this series reworks the system heap to use sgtables, and then
consolidates the pagelist method from the heap-helpers into the
CMA heap. After which the heap-helpers logic is removed (as it
is unused). I'd still like to find a better way to avoid some of
the logic duplication in implementing the entire dma_buf_ops
handlers per heap. But unfortunately that code is tied somewhat
to how the buffer's memory is tracked.

After this, the series introduces two optimizations to the the
system heap, utilizing large order pages, and adding a page-pool
(maybe abusing the pagepool logic from the network code, but it
seems silly to reimplement it).


I implemented a simple allocation microbenchmark to compare
dmabuf heaps vs ion:
  https://git.linaro.org/people/john.stultz/android-dev.git/commit/?h=dev/dma-buf-heap-perf&id=e33aabd34b300f8f8be8d71ec7253dd0abe702f2

With these changes, the allocation path is *much* improved,
performing better then ION (though to be fair, the repeated 
allocating and freeing of the same size buffer is the ideal
case for the pagepool logic, so don't read too much into it).

I charted some datapoints from the microbenchmark with each
of the patches should folks be interested.
https://docs.google.com/spreadsheets/d/1-1C8ZQpmkl_0DISkI6z4xelE08MlNAN7oEu34AnO4Ao/edit#gid=0

Finally, a port of a patch that Ørjan Eide implemented for ION
that avoids calling sync on attachments that don't have a
mapping.

Feedback on these would be great!


Cc: Sumit Semwal <sumit.semwal at linaro.org>
Cc: Liam Mark <lmark at codeaurora.org>
Cc: Laura Abbott <labbott at kernel.org>
Cc: Brian Starkey <Brian.Starkey at arm.com>
Cc: Hridya Valsaraju <hridya at google.com>
Cc: Suren Baghdasaryan <surenb at google.com>
Cc: Sandeep Patil <sspatil at google.com>
Cc: Ørjan Eide <orjan.eide at arm.com>
Cc: Robin Murphy <robin.murphy at arm.com>
Cc: Ezequiel Garcia <ezequiel at collabora.com>
Cc: Simon Ser <contact at emersion.fr>
Cc: James Jones <jajones at nvidia.com>
Cc: linux-media at vger.kernel.org
Cc: dri-devel at lists.freedesktop.org

John Stultz (6):
  dma-buf: system_heap: Rework system heap to use sgtables instead of
    pagelists
  dma-buf: heaps: Move heap-helper logic into the cma_heap
    implementation
  dma-buf: heaps: Remove heap-helpers code
  dma-buf: system_heap: Allocate higher order pages if available
  dma-buf: system_heap: Add pagepool support to system heap
  dma-buf: heaps: Skip sync if not mapped

 drivers/dma-buf/heaps/Kconfig        |   1 +
 drivers/dma-buf/heaps/Makefile       |   1 -
 drivers/dma-buf/heaps/cma_heap.c     | 332 +++++++++++++++++----
 drivers/dma-buf/heaps/heap-helpers.c | 271 -----------------
 drivers/dma-buf/heaps/heap-helpers.h |  53 ----
 drivers/dma-buf/heaps/system_heap.c  | 426 ++++++++++++++++++++++++---
 6 files changed, 660 insertions(+), 424 deletions(-)
 delete mode 100644 drivers/dma-buf/heaps/heap-helpers.c
 delete mode 100644 drivers/dma-buf/heaps/heap-helpers.h

-- 
2.17.1