[Xen-devel] Re: [PATCH] TTM DMA pool v2.1

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Oct 19, 2011 at 06:19:21PM -0400, Konrad Rzeszutek Wilk wrote:

Hmm, seems a part of this got eaten by the Internet monsters.

Since v2.0: [not posted]
 - Redid the registration/override to be tightly integrated with the
   'struct ttm_backend_func' per Thomas's suggestion.
Since v1.9: [not posted]
 - Performance improvements - it was doing O(n^2) instead of O(n) on certain
   workloads.
Since v1.8: [lwn.net/Articles/458724/]
 - Removed swiotlb_enabled and used swiotlb_nr_tbl.
 - Added callback for changing cache types.
Since v1.7: [https://lkml.org/lkml/2011/8/30/460]
 - Fixed checking the DMA address in radeon/nouveau code.
Since v1: [http://lwn.net/Articles/456246/]
 - Ran it through the gauntlet of SubmitChecklist and fixed issues
 - Made radeon/nouveau driver set coherent_dma (which is required for dmapool)

> [.. and this is what I said in v1 post]:
> 
> Way back in January this patchset:
> http://lists.freedesktop.org/archives/dri-devel/2011-January/006905.html
> 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@xxxxxxxxxxxx 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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