Re: [PATCH 27/33] dma-direct: use node local allocations for coherent memory

[Robin Murphy]

On 10/01/18 15:30, Christoph Hellwig wrote:

On Wed, Jan 10, 2018 at 12:06:22PM +, Robin Murphy wrote:

On 10/01/18 08:00, Christoph Hellwig wrote:

To preserve the x86 behavior.


And combined with patch 10/22 of the SWIOTLB refactoring, this means
SWIOTLB allocations will also end up NUMA-aware, right? Great, that's what
we want on arm64 too :)


Well, only for swiotlb allocations that can be satisfied by
dma_direct_alloc.  If we actually have to fall back to the swiotlb
buffers there is not node affinity yet.


Yeah, when I looked into it I reached the conclusion that per-node 
bounce buffers probably weren't worth it - if you have to bounce you've 
already pretty much lost the performance game, and if the CPU doing the 
bouncing happens to be on a different node from the device you've 
certainly lost either way. Per-node CMA zones we definitely *would* 
like, but that's a future problem (it looks technically feasible without 
huge infrastructure changes, but fiddly).


Robin.
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Re: [PATCH 27/33] dma-direct: use node local allocations for coherent memory

[Christoph Hellwig]

On Wed, Jan 10, 2018 at 12:06:22PM +, Robin Murphy wrote:
> On 10/01/18 08:00, Christoph Hellwig wrote:
>> To preserve the x86 behavior.
>
> And combined with patch 10/22 of the SWIOTLB refactoring, this means 
> SWIOTLB allocations will also end up NUMA-aware, right? Great, that's what 
> we want on arm64 too :)

Well, only for swiotlb allocations that can be satisfied by
dma_direct_alloc.  If we actually have to fall back to the swiotlb
buffers there is not node affinity yet.
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Re: [PATCH 27/33] dma-direct: use node local allocations for coherent memory

[Robin Murphy]

On 10/01/18 08:00, Christoph Hellwig wrote:

To preserve the x86 behavior.


And combined with patch 10/22 of the SWIOTLB refactoring, this means 
SWIOTLB allocations will also end up NUMA-aware, right? Great, that's 
what we want on arm64 too :)


Reviewed-by: Robin Murphy 


Signed-off-by: Christoph Hellwig 
---
  lib/dma-direct.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index a9ae98be7af3..f04a424f91fa 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -38,7 +38,7 @@ static void *dma_direct_alloc(struct device *dev, size_t size,
if (gfpflags_allow_blocking(gfp))
page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
if (!page)
-   page = alloc_pages(gfp, page_order);
+   page = alloc_pages_node(dev_to_node(dev), gfp, page_order);
if (!page)
return NULL;
  


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[PATCH 27/33] dma-direct: use node local allocations for coherent memory

[Christoph Hellwig]

To preserve the x86 behavior.

Signed-off-by: Christoph Hellwig 
---
 lib/dma-direct.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index a9ae98be7af3..f04a424f91fa 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -38,7 +38,7 @@ static void *dma_direct_alloc(struct device *dev, size_t size,
if (gfpflags_allow_blocking(gfp))
page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
if (!page)
-   page = alloc_pages(gfp, page_order);
+   page = alloc_pages_node(dev_to_node(dev), gfp, page_order);
if (!page)
return NULL;
 
-- 
2.14.2

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