Re: [PATCH 00/13] Rework IOMMU API to allow for batching of invalidation

[John Garry <john.garry@huawei.com>]

On 14/08/2019 18:56, Will Deacon wrote:
> Hi everybody,
>
> These are the core IOMMU changes that I have posted previously as part
> of my ongoing effort to reduce the lock contention of the SMMUv3 command
> queue. I thought it would be better to split this out as a separate
> series, since I think it's ready to go and all the driver conversions
> mean that it's quite a pain for me to maintain out of tree!
>
> The idea of the patch series is to allow TLB invalidation to be batched
> up into a new 'struct iommu_iotlb_gather' structure, which tracks the
> properties of the virtual address range being invalidated so that it
> can be deferred until the driver's ->iotlb_sync() function is called.
> This allows for more efficient invalidation on hardware that can submit
> multiple invalidations in one go.
>
> The previous series was included in:
>
>   https://lkml.kernel.org/r/20190711171927.28803-1-will@kernel.org
>
> The only real change since then is incorporating the newly merged
> virtio-iommu driver.
>
> If you'd like to play with the patches, then I've also pushed them here:
>
>   https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=iommu/unmap
>
> but they should behave as a no-op on their own.

Hi Will,

As anticipated, my storage testing scenarios roughly give parity 
throughput and CPU loading before and after this series.

Patches to convert the
> Arm SMMUv3 driver to the new API are here:
>
>   https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=iommu/cmdq

I quickly tested this again and now I see a performance lift:

			before (5.3-rc1)		after
D05 8x SAS disks	907K IOPS			970K IOPS
D05 1x NVMe		450K IOPS			466K IOPS
D06 1x NVMe		467K IOPS			466K IOPS

The CPU loading seems to track throughput, so nothing much to say there.

Note: From 5.2 testing, I was seeing >900K IOPS from that NVMe disk for 
!IOMMU.

BTW, what were your thoughts on changing 
arm_smmu_atc_inv_domain()->arm_smmu_atc_inv_master() to batching? It 
seems suitable, but looks untouched. Were you waiting for a resolution 
to the performance issue which Leizhen reported?

Thanks,
John

>
> Cheers,
>
> Will
>
> --->8
>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Jayachandran Chandrasekharan Nair <jnair@marvell.com>
> Cc: Jan Glauber <jglauber@marvell.com>
> Cc: Jon Masters <jcm@redhat.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Zhen Lei <thunder.leizhen@huawei.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Vijay Kilary <vkilari@codeaurora.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: John Garry <john.garry@huawei.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: David Woodhouse <dwmw2@infradead.org>
>
> Will Deacon (13):
>   iommu: Remove empty iommu_tlb_range_add() callback from iommu_ops
>   iommu/io-pgtable-arm: Remove redundant call to io_pgtable_tlb_sync()
>   iommu/io-pgtable: Rename iommu_gather_ops to iommu_flush_ops
>   iommu: Introduce struct iommu_iotlb_gather for batching TLB flushes
>   iommu: Introduce iommu_iotlb_gather_add_page()
>   iommu: Pass struct iommu_iotlb_gather to ->unmap() and ->iotlb_sync()
>   iommu/io-pgtable: Introduce tlb_flush_walk() and tlb_flush_leaf()
>   iommu/io-pgtable: Hook up ->tlb_flush_walk() and ->tlb_flush_leaf() in
>     drivers
>   iommu/io-pgtable-arm: Call ->tlb_flush_walk() and ->tlb_flush_leaf()
>   iommu/io-pgtable: Replace ->tlb_add_flush() with ->tlb_add_page()
>   iommu/io-pgtable: Remove unused ->tlb_sync() callback
>   iommu/io-pgtable: Pass struct iommu_iotlb_gather to ->unmap()
>   iommu/io-pgtable: Pass struct iommu_iotlb_gather to ->tlb_add_page()
>
>  drivers/gpu/drm/panfrost/panfrost_mmu.c |  24 +++++---
>  drivers/iommu/amd_iommu.c               |  11 ++--
>  drivers/iommu/arm-smmu-v3.c             |  52 +++++++++++-----
>  drivers/iommu/arm-smmu.c                | 103 ++++++++++++++++++++++++--------
>  drivers/iommu/dma-iommu.c               |   9 ++-
>  drivers/iommu/exynos-iommu.c            |   3 +-
>  drivers/iommu/intel-iommu.c             |   3 +-
>  drivers/iommu/io-pgtable-arm-v7s.c      |  57 +++++++++---------
>  drivers/iommu/io-pgtable-arm.c          |  48 ++++++++-------
>  drivers/iommu/iommu.c                   |  24 ++++----
>  drivers/iommu/ipmmu-vmsa.c              |  28 +++++----
>  drivers/iommu/msm_iommu.c               |  42 +++++++++----
>  drivers/iommu/mtk_iommu.c               |  45 +++++++++++---
>  drivers/iommu/mtk_iommu_v1.c            |   3 +-
>  drivers/iommu/omap-iommu.c              |   2 +-
>  drivers/iommu/qcom_iommu.c              |  44 +++++++++++---
>  drivers/iommu/rockchip-iommu.c          |   2 +-
>  drivers/iommu/s390-iommu.c              |   3 +-
>  drivers/iommu/tegra-gart.c              |  12 +++-
>  drivers/iommu/tegra-smmu.c              |   2 +-
>  drivers/iommu/virtio-iommu.c            |   5 +-
>  drivers/vfio/vfio_iommu_type1.c         |  27 +++++----
>  include/linux/io-pgtable.h              |  57 ++++++++++++------
>  include/linux/iommu.h                   |  92 +++++++++++++++++++++-------
>  24 files changed, 483 insertions(+), 215 deletions(-)
>


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