From: Catalin Marinas <catalin.marinas@arm.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Arnd Bergmann <arnd@arndb.de>, Christoph Hellwig <hch@lst.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
Ard Biesheuvel <ardb@kernel.org>,
Isaac Manjarres <isaacmanjarres@google.com>,
Saravana Kannan <saravanak@google.com>,
Alasdair Kergon <agk@redhat.com>, Daniel Vetter <daniel@ffwll.ch>,
Joerg Roedel <joro@8bytes.org>, Mark Brown <broonie@kernel.org>,
Mike Snitzer <snitzer@kernel.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
linux-mm@kvack.org, iommu@lists.linux.dev,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 13/13] dma: arm64: Add CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC and enable it for arm64
Date: Tue, 8 Nov 2022 09:52:15 +0000 [thread overview]
Message-ID: <Y2omz6pibSUNPtHu@arm.com> (raw)
In-Reply-To: <6e846f75-b330-9523-4356-41d5f9e48f12@arm.com>
On Mon, Nov 07, 2022 at 01:03:31PM +0000, Robin Murphy wrote:
> On 2022-11-06 22:01, Catalin Marinas wrote:
> > With all the infrastructure in place for bouncing small kmalloc()
> > buffers, add the corresponding Kconfig entry and select it for arm64.
>
> AFAICS we're missing the crucial part to ensure that SWIOTLB is available
> even when max_pfn <= arm64_dma_phys_limit, which is very likely to be true
> on low-memory systems that care most about kmalloc wastage.
This was a deliberate decision for this version. Patch 4 mitigates it a
bit by raising the kmalloc() minimum alignment to the cache line size
(typically 64). It's still an improvement from the current 128-byte
alignment.
Since it's hard to guess the optimal swiotlb buffer for such platforms,
I think a follow-up step would be to use the DMA coherent pool for
bouncing if no swiotlb buffer is available. At least the pool can grow
dynamically. Yet another option would be to increase the swiotlb buffer
at run-time but it has an overhead for is_swiotlb_buffer().
--
Catalin
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next prev parent reply other threads:[~2022-11-08 9:53 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-06 22:01 [PATCH v3 00/13] mm, dma, arm64: Reduce ARCH_KMALLOC_MINALIGN to 8 Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 01/13] mm/slab: Decouple ARCH_KMALLOC_MINALIGN from ARCH_DMA_MINALIGN Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 02/13] dma-mapping: Force bouncing if the kmalloc() size is not cacheline-aligned Catalin Marinas
2022-11-07 9:43 ` Christoph Hellwig
2022-11-06 22:01 ` [PATCH v3 03/13] iommu/dma: Force bouncing of the " Catalin Marinas
2022-11-07 9:46 ` Christoph Hellwig
2022-11-07 10:54 ` Catalin Marinas
2022-11-07 13:26 ` Robin Murphy
2022-11-08 10:51 ` Catalin Marinas
2022-11-08 11:40 ` Robin Murphy
2022-11-08 7:50 ` Christoph Hellwig
2022-11-14 23:23 ` Isaac Manjarres
2022-11-15 11:48 ` Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 04/13] mm/slab: Allow kmalloc() minimum alignment fallback to dma_get_cache_alignment() Catalin Marinas
[not found] ` <202211070812.BhGKB0Hd-lkp@intel.com>
2022-11-07 9:22 ` Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 05/13] mm/slab: Simplify create_kmalloc_cache() args and make it static Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 06/13] dma: Allow the smaller cache_line_size() returned by dma_get_cache_alignment() Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 07/13] drivers/base: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 08/13] drivers/gpu: " Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 09/13] drivers/usb: " Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 10/13] drivers/spi: " Catalin Marinas
2022-11-07 12:58 ` Mark Brown
2022-11-06 22:01 ` [PATCH v3 11/13] crypto: " Catalin Marinas
2022-11-07 2:22 ` Herbert Xu
2022-11-07 9:05 ` Catalin Marinas
2022-11-07 9:12 ` Herbert Xu
2022-11-07 9:38 ` Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 12/13] drivers/md: " Catalin Marinas
2022-11-06 22:01 ` [PATCH v3 13/13] dma: arm64: Add CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC and enable it for arm64 Catalin Marinas
2022-11-07 13:03 ` Robin Murphy
2022-11-07 14:38 ` Christoph Hellwig
2022-11-07 15:24 ` Robin Murphy
2022-11-08 9:52 ` Catalin Marinas [this message]
2022-11-08 10:03 ` Christoph Hellwig
2022-11-30 18:48 ` Isaac Manjarres
2022-11-30 23:32 ` Alexander Graf
2023-04-20 11:51 ` Petr Tesařík
2023-03-16 18:38 ` [PATCH v3 00/13] mm, dma, arm64: Reduce ARCH_KMALLOC_MINALIGN to 8 Isaac Manjarres
2023-04-19 16:06 ` Catalin Marinas
2023-04-20 9:52 ` Petr Tesarik
2023-04-20 17:43 ` Catalin Marinas
2023-05-15 19:09 ` Isaac Manjarres
2023-05-16 17:19 ` Catalin Marinas
2023-05-16 18:19 ` Isaac Manjarres
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