When debugging is disabled, kzalloc returns page-aligned
addresses:
Is it defined some where that regular kzalloc/kmalloc guaranties to
return a page-aligned address as you see in your testing ? if so the
debug mode should behave the same. Otherwise we can consider using any
flag allocation that can force that if such exists.
Let's get other people's input here.
My understanding is that the fact that k[mz]alloc() returns a page-aligned buffer if the allocation size is > PAGE_SIZE / 2 is a side effect of the implementation and not something callers of that function should rely on. I think the only assumption k[mz]alloc() callers should rely on is that the allocated memory respects ARCH_KMALLOC_MINALIGN.
I agree. mlx4_alloc_priv_pages() is carefully designed to
correct the alignment of the buffer, so it already assumes
that it is not getting a page-aligned buffer.
The alignment isn't the problem here, though. It's that
the buffer contains a page-boundary. That is guaranteed
to be the case for HCAs that support more than 512
sges, so that will have to be addressed (at least in
mlx5).
rrr...
I think we should make the pages allocations dma coherent
in order to fix that...
Nice catch Chunk.
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