[PATCH] TTM DMA pool v2.1

Konrad Rzeszutek Wilk konrad.wilk at oracle.com
Wed Oct 19 15:19:21 PDT 2011

[.. and this is what I said in v1 post]:

Way back in January this patchset:
was merged in, but pieces of it had to be reverted b/c they did not
work properly under PowerPC, ARM, and when swapping out pages to disk.

After a bit of discussion on the mailing list
http://marc.info/?i=4D769726.2030307@shipmail.org I started working on it, but
got waylaid by other things .. and finally I am able to post the RFC patches.

There was a lot of discussion about it and I am not sure if I captured
everybody's thoughts - if I did not - that is _not_ intentional - it has just
been quite some time..

Anyhow .. the patches explore what the "lib/dmapool.c" does - which is to have a
DMA pool that the device has associated with. I kind of married that code
along with drivers/gpu/drm/ttm/ttm_page_alloc.c to create a TTM DMA pool code.
The end result is DMA pool with extra features: can do write-combine, uncached,
writeback (and tracks them and sets back to WB when freed); tracks "cached"
pages that don't really need to be returned to a pool; and hooks up to
the shrinker code so that the pools can be shrunk.

If you guys think this set of patches make sense  - my future plans were
 1) Get this in large crowd of testing .. and if it works for a kernel release
 2) to move a bulk of this in the lib/dmapool.c (I spoke with Matthew Wilcox
    about it and he is OK as long as I don't introduce performance regressions).

But before I do any of that a second set of eyes taking a look at these
patches would be most welcome.

In regards to testing, I've been running them non-stop for the last month.
(and found some issues which I've fixed up) - and been quite happy with how
they work.

Michel (thanks!) took a spin of the patches on his PowerPC and they did not
cause any regressions (wheew).

The patches are also located in a git tree:

 git://oss.oracle.com/git/kwilk/xen.git devel/ttm.dma_pool.v2.1

Konrad Rzeszutek Wilk (11):
      swiotlb: Expose swiotlb_nr_tlb function to modules
      nouveau/radeon: Set coherent DMA mask
      ttm/radeon/nouveau: Check the DMA address from TTM against known value.
      ttm: Wrap ttm_[put|get]_pages and extract GFP_* and caching states from 'struct ttm_tt'
      ttm: Get rid of temporary scaffolding
      ttm/driver: Expand ttm_backend_func to include two overrides for TTM page pool.
      ttm: Do not set the ttm->be to NULL before calling the TTM page pool to free pages.
      ttm: Provide DMA aware TTM page pool code.
      ttm: Add 'no_dma' parameter to turn the TTM DMA pool off during runtime.
      nouveau/ttm/dma: Enable the TTM DMA pool if device can only do 32-bit DMA.
      radeon/ttm/dma: Enable the TTM DMA pool if the device can only do 32-bit.

 drivers/gpu/drm/nouveau/nouveau_debugfs.c |    1 +
 drivers/gpu/drm/nouveau/nouveau_mem.c     |    5 +
 drivers/gpu/drm/nouveau/nouveau_sgdma.c   |    8 +-
 drivers/gpu/drm/radeon/radeon_device.c    |    6 +
 drivers/gpu/drm/radeon/radeon_gart.c      |    4 +-
 drivers/gpu/drm/radeon/radeon_ttm.c       |   19 +-
 drivers/gpu/drm/ttm/Makefile              |    3 +
 drivers/gpu/drm/ttm/ttm_memory.c          |    5 +
 drivers/gpu/drm/ttm/ttm_page_alloc.c      |  108 ++-
 drivers/gpu/drm/ttm/ttm_page_alloc_dma.c  | 1446 +++++++++++++++++++++++++++++
 drivers/gpu/drm/ttm/ttm_tt.c              |   21 +-
 drivers/xen/swiotlb-xen.c                 |    2 +-
 include/drm/ttm/ttm_bo_driver.h           |   31 +
 include/drm/ttm/ttm_page_alloc.h          |   53 +-
 include/linux/swiotlb.h                   |    2 +-
 lib/swiotlb.c                             |    5 +-
 16 files changed, 1637 insertions(+), 82 deletions(-)

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