On Wed, 24 May 2023 18:18:49 +0100
Catalin Marinas <catalin.marinas@xxxxxxx> wrote:
> Hi,
>
> Another version of the series reducing the kmalloc() minimum alignment
> on arm64 to 8 (from 128). Other architectures can easily opt in by
> defining ARCH_KMALLOC_MINALIGN as 8 and selecting
> DMA_BOUNCE_UNALIGNED_KMALLOC.
>
> The first 10 patches decouple ARCH_KMALLOC_MINALIGN from
> ARCH_DMA_MINALIGN and, for arm64, limit the kmalloc() caches to those
> aligned to the run-time probed cache_line_size(). On arm64 we gain the
> kmalloc-{64,192} caches.
>
> The subsequent patches (11 to 15) further reduce the kmalloc() caches to
> kmalloc-{8,16,32,96} if the default swiotlb is present by bouncing small
> buffers in the DMA API.
Hi Catalin,
I think IIO_DMA_MINALIGN needs to switch to ARCH_DMA_MINALIGN as well.
It's used to force static alignement of buffers with larger structures,
to make them suitable for non coherent DMA, similar to your other cases.
Thanks,
Jonathan
>
> Changes since v4:
>
> - Following Robin's suggestions, reworked the iommu handling so that the
> buffer size checks are done in the dev_use_swiotlb() and
> dev_use_sg_swiotlb() functions (together with dev_is_untrusted()). The
> sync operations can now check for the SG_DMA_USE_SWIOTLB flag. Since
> this flag is no longer specific to kmalloc() bouncing (covers
> dev_is_untrusted() as well), the sg_is_dma_use_swiotlb() and
> sg_dma_mark_use_swiotlb() functions are always defined if
> CONFIG_SWIOTLB.
>
> - Dropped ARCH_WANT_KMALLOC_DMA_BOUNCE, only left the
> DMA_BOUNCE_UNALIGNED_KMALLOC option, selectable by the arch code. The
> NEED_SG_DMA_FLAGS is now selected by IOMMU_DMA if SWIOTLB.
>
> - Rather than adding another config option, allow
> dma_get_cache_alignment() to be overridden by the arch code
> (Christoph's suggestion).
>
> - Added a comment to the dma_kmalloc_needs_bounce() function on the
> heuristics behind the bouncing.
>
> - Added acked-by/reviewed-by tags (not adding Ard's tested-by yet as
> there were some changes).
>
> The updated patches are also available on this branch:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux devel/kmalloc-minalign
>
> Thanks.
>
> Catalin Marinas (14):
> mm/slab: Decouple ARCH_KMALLOC_MINALIGN from ARCH_DMA_MINALIGN
> dma: Allow dma_get_cache_alignment() to be overridden by the arch code
> mm/slab: Simplify create_kmalloc_cache() args and make it static
> mm/slab: Limit kmalloc() minimum alignment to
> dma_get_cache_alignment()
> drivers/base: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN
> drivers/gpu: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN
> drivers/usb: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN
> drivers/spi: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN
> drivers/md: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN
> arm64: Allow kmalloc() caches aligned to the smaller cache_line_size()
> dma-mapping: Force bouncing if the kmalloc() size is not
> cache-line-aligned
> iommu/dma: Force bouncing if the size is not cacheline-aligned
> mm: slab: Reduce the kmalloc() minimum alignment if DMA bouncing
> possible
> arm64: Enable ARCH_WANT_KMALLOC_DMA_BOUNCE for arm64
>
> Robin Murphy (1):
> scatterlist: Add dedicated config for DMA flags
>
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/cache.h | 3 ++
> arch/arm64/mm/init.c | 7 +++-
> drivers/base/devres.c | 6 ++--
> drivers/gpu/drm/drm_managed.c | 6 ++--
> drivers/iommu/Kconfig | 1 +
> drivers/iommu/dma-iommu.c | 50 +++++++++++++++++++++++-----
> drivers/md/dm-crypt.c | 2 +-
> drivers/pci/Kconfig | 1 +
> drivers/spi/spidev.c | 2 +-
> drivers/usb/core/buffer.c | 8 ++---
> include/linux/dma-map-ops.h | 61 ++++++++++++++++++++++++++++++++++
> include/linux/dma-mapping.h | 4 ++-
> include/linux/scatterlist.h | 29 +++++++++++++---
> include/linux/slab.h | 14 ++++++--
> kernel/dma/Kconfig | 7 ++++
> kernel/dma/direct.h | 3 +-
> mm/slab.c | 6 +---
> mm/slab.h | 5 ++-
> mm/slab_common.c | 46 +++++++++++++++++++------
> 20 files changed, 213 insertions(+), 49 deletions(-)
>
>
>
