Re: [PATCH v5 0/7] dma-buf: Performance improvements for system heap & a system-uncached implementation

[Sumit Semwal]

Hi John,

On Tue, 10 Nov 2020 at 09:19, John Stultz <john.stultz@xxxxxxxxxx> wrote:
>
> Hey All,
>   So just wanted to send my last revision of my patch series
> of performance optimizations to the dma-buf system heap.

Thanks very much for your patches - I think the first 5 patches look good to me.

I know there was a bit of discussion over adding a new system-uncached
heap v/s using a flag to identify that; I think I prefer the separate
heap idea, but lets ask one last time if any one else has any real
objections to it.

Daniel, Christian: any comments from your side on this?

I am planning to merge this series to drm-misc this week if I hear no
objections.
>
> 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. As more heaps show up I
> think we'll have a better idea how to best share code, so for
> now I think this is ok.
>
> After this, the series introduces an optimization that
> Ørjan Eide implemented for ION that avoids calling sync on
> attachments that don't have a mapping.
>
> Next, an optimization to use larger order pages for the system
> heap. This change brings us closer to the current performance
> of the ION allocation code (though there still is a gap due
> to ION using a mix of deferred-freeing and page pools, I'll be
> looking at integrating those eventually).
>
> Finally, a reworked version of my uncached system heap
> implementation I was submitting a few weeks back. Since it
> duplicated a lot of the now reworked system heap code, I
> realized it would be much simpler to add the functionality to
> the system_heap implementation itself.
>
> While not improving the core allocation performance, the
> uncached heap allocations do result in *much* improved
> performance on HiKey960 as it avoids a lot of flushing and
> invalidating buffers that the cpu doesn't touch often.
>
> Feedback on these would be great!
>
> thanks
> -john
>
> New in v5:
> * Added a comment explaining why the order sizes are
>   chosen as they are
>
> Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> Cc: Liam Mark <lmark@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: Chris Goldsworthy <cgoldswo@xxxxxxxxxxxxxx>
> 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):
>   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: heaps: Skip sync if not mapped
>   dma-buf: system_heap: Allocate higher order pages if available
>   dma-buf: dma-heap: Keep track of the heap device struct
>   dma-buf: system_heap: Add a system-uncached heap re-using the system
>     heap
>
>  drivers/dma-buf/dma-heap.c           |  33 +-
>  drivers/dma-buf/heaps/Makefile       |   1 -
>  drivers/dma-buf/heaps/cma_heap.c     | 324 +++++++++++++++---
>  drivers/dma-buf/heaps/heap-helpers.c | 270 ---------------
>  drivers/dma-buf/heaps/heap-helpers.h |  53 ---
>  drivers/dma-buf/heaps/system_heap.c  | 494 ++++++++++++++++++++++++---
>  include/linux/dma-heap.h             |   9 +
>  7 files changed, 753 insertions(+), 431 deletions(-)
>  delete mode 100644 drivers/dma-buf/heaps/heap-helpers.c
>  delete mode 100644 drivers/dma-buf/heaps/heap-helpers.h
>
> --
> 2.17.1
>
Thanks much,

Best,
Sumit.