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From: Joerg Roedel <joro@8bytes.org>
To: David Stevens <stevensd@chromium.org>,
	Robin Murphy <robin.murphy@arm.com>
Cc: Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	David Stevens <stevensd@google.com>
Subject: Re: [PATCH 0/4] Add dynamic iommu backed bounce buffers
Date: Thu, 8 Jul 2021 11:29:18 +0200	[thread overview]
Message-ID: <YObFbqEk1nGVuHLF@8bytes.org> (raw)
In-Reply-To: <20210707075505.2896824-1-stevensd@google.com>

Adding Robin too.

On Wed, Jul 07, 2021 at 04:55:01PM +0900, David Stevens wrote:
> Add support for per-domain dynamic pools of iommu bounce buffers to the 
> dma-iommu API. This allows iommu mappings to be reused while still
> maintaining strict iommu protection. Allocating buffers dynamically
> instead of using swiotlb carveouts makes per-domain pools more amenable
> on systems with large numbers of devices or where devices are unknown.
> 
> When enabled, all non-direct streaming mappings below a configurable
> size will go through bounce buffers. Note that this means drivers which
> don't properly use the DMA API (e.g. i915) cannot use an iommu when this
> feature is enabled. However, all drivers which work with swiotlb=force
> should work.
> 
> Bounce buffers serve as an optimization in situations where interactions
> with the iommu are very costly. For example, virtio-iommu operations in
> a guest on a linux host require a vmexit, involvement the VMM, and a
> VFIO syscall. For relatively small DMA operations, memcpy can be
> significantly faster.
> 
> As a performance comparison, on a device with an i5-10210U, I ran fio
> with a VFIO passthrough NVMe drive with '--direct=1 --rw=read
> --ioengine=libaio --iodepth=64' and block sizes 4k, 16k, 64k, and
> 128k. Test throughput increased by 2.8x, 4.7x, 3.6x, and 3.6x. Time
> spent in iommu_dma_unmap_(page|sg) per GB processed decreased by 97%,
> 94%, 90%, and 87%. Time spent in iommu_dma_map_(page|sg) decreased
> by >99%, as bounce buffers don't require syncing here in the read case.
> Running with multiple jobs doesn't serve as a useful performance
> comparison because virtio-iommu and vfio_iommu_type1 both have big
> locks that significantly limit mulithreaded DMA performance.
> 
> This patch set is based on v5.13-rc7 plus the patches at [1].
> 
> David Stevens (4):
>   dma-iommu: add kalloc gfp flag to alloc helper
>   dma-iommu: replace device arguments
>   dma-iommu: expose a few helper functions to module
>   dma-iommu: Add iommu bounce buffers to dma-iommu api
> 
>  drivers/iommu/Kconfig          |  10 +
>  drivers/iommu/Makefile         |   1 +
>  drivers/iommu/dma-iommu.c      | 119 ++++--
>  drivers/iommu/io-buffer-pool.c | 656 +++++++++++++++++++++++++++++++++
>  drivers/iommu/io-buffer-pool.h |  91 +++++
>  include/linux/dma-iommu.h      |  12 +
>  6 files changed, 861 insertions(+), 28 deletions(-)
>  create mode 100644 drivers/iommu/io-buffer-pool.c
>  create mode 100644 drivers/iommu/io-buffer-pool.h
> 
> -- 
> 2.32.0.93.g670b81a890-goog

WARNING: multiple messages have this Message-ID
From: Joerg Roedel <joro@8bytes.org>
To: David Stevens <stevensd@chromium.org>,
	Robin Murphy <robin.murphy@arm.com>
Cc: David Stevens <stevensd@google.com>,
	linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	iommu@lists.linux-foundation.org, Will Deacon <will@kernel.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 0/4] Add dynamic iommu backed bounce buffers
Date: Thu, 8 Jul 2021 11:29:18 +0200	[thread overview]
Message-ID: <YObFbqEk1nGVuHLF@8bytes.org> (raw)
In-Reply-To: <20210707075505.2896824-1-stevensd@google.com>

Adding Robin too.

On Wed, Jul 07, 2021 at 04:55:01PM +0900, David Stevens wrote:
> Add support for per-domain dynamic pools of iommu bounce buffers to the 
> dma-iommu API. This allows iommu mappings to be reused while still
> maintaining strict iommu protection. Allocating buffers dynamically
> instead of using swiotlb carveouts makes per-domain pools more amenable
> on systems with large numbers of devices or where devices are unknown.
> 
> When enabled, all non-direct streaming mappings below a configurable
> size will go through bounce buffers. Note that this means drivers which
> don't properly use the DMA API (e.g. i915) cannot use an iommu when this
> feature is enabled. However, all drivers which work with swiotlb=force
> should work.
> 
> Bounce buffers serve as an optimization in situations where interactions
> with the iommu are very costly. For example, virtio-iommu operations in
> a guest on a linux host require a vmexit, involvement the VMM, and a
> VFIO syscall. For relatively small DMA operations, memcpy can be
> significantly faster.
> 
> As a performance comparison, on a device with an i5-10210U, I ran fio
> with a VFIO passthrough NVMe drive with '--direct=1 --rw=read
> --ioengine=libaio --iodepth=64' and block sizes 4k, 16k, 64k, and
> 128k. Test throughput increased by 2.8x, 4.7x, 3.6x, and 3.6x. Time
> spent in iommu_dma_unmap_(page|sg) per GB processed decreased by 97%,
> 94%, 90%, and 87%. Time spent in iommu_dma_map_(page|sg) decreased
> by >99%, as bounce buffers don't require syncing here in the read case.
> Running with multiple jobs doesn't serve as a useful performance
> comparison because virtio-iommu and vfio_iommu_type1 both have big
> locks that significantly limit mulithreaded DMA performance.
> 
> This patch set is based on v5.13-rc7 plus the patches at [1].
> 
> David Stevens (4):
>   dma-iommu: add kalloc gfp flag to alloc helper
>   dma-iommu: replace device arguments
>   dma-iommu: expose a few helper functions to module
>   dma-iommu: Add iommu bounce buffers to dma-iommu api
> 
>  drivers/iommu/Kconfig          |  10 +
>  drivers/iommu/Makefile         |   1 +
>  drivers/iommu/dma-iommu.c      | 119 ++++--
>  drivers/iommu/io-buffer-pool.c | 656 +++++++++++++++++++++++++++++++++
>  drivers/iommu/io-buffer-pool.h |  91 +++++
>  include/linux/dma-iommu.h      |  12 +
>  6 files changed, 861 insertions(+), 28 deletions(-)
>  create mode 100644 drivers/iommu/io-buffer-pool.c
>  create mode 100644 drivers/iommu/io-buffer-pool.h
> 
> -- 
> 2.32.0.93.g670b81a890-goog
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  parent reply	other threads:[~2021-07-08  9:29 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-07  7:55 David Stevens
2021-07-07  7:55 ` David Stevens
2021-07-07  7:55 ` [PATCH 1/4] dma-iommu: add kalloc gfp flag to alloc helper David Stevens
2021-07-07  7:55   ` David Stevens
2021-07-08 17:22   ` Robin Murphy
2021-07-08 17:22     ` Robin Murphy
2021-07-07  7:55 ` [PATCH 2/4] dma-iommu: replace device arguments David Stevens
2021-07-07  7:55   ` David Stevens
2021-07-07  7:55 ` [PATCH 3/4] dma-iommu: expose a few helper functions to module David Stevens
2021-07-07  7:55   ` David Stevens
2021-07-07  7:55 ` [PATCH 4/4] dma-iommu: Add iommu bounce buffers to dma-iommu api David Stevens
2021-07-07  7:55   ` David Stevens
2021-07-08  9:29 ` Joerg Roedel [this message]
2021-07-08  9:29   ` [PATCH 0/4] Add dynamic iommu backed bounce buffers Joerg Roedel
2021-07-08 17:14   ` Robin Murphy
2021-07-08 17:14     ` Robin Murphy
2021-07-09  7:25     ` David Stevens
2021-07-09  7:25       ` David Stevens
2021-07-08 13:38 ` Lu Baolu
2021-07-08 13:38   ` Lu Baolu
2021-07-09  6:04   ` David Stevens
2021-07-09  6:04     ` David Stevens

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