From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: linux-arm-kernel@lists.infradead.org,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>
Subject: SMMU performance
Date: Mon, 30 Sep 2019 12:00:47 +0100 [thread overview]
Message-ID: <20190930110047.GF25745@shell.armlinux.org.uk> (raw)
Hi,
While using iperf on a platform using the ARM SMMU (v2), I notice the
following behaviour on v5.3 with Will's iommu patch set merged, kernel
lock debugging disabled.
With iommu.passthrough=1, three consecutive runs:
[ 3] 0.0-10.0 sec 4.51 GBytes 3.87 Gbits/sec
[ 3] 0.0-10.0 sec 4.53 GBytes 3.89 Gbits/sec
[ 3] 0.0-10.0 sec 4.49 GBytes 3.86 Gbits/sec
With iommu.passthrough=0:
[ 3] 0.0-10.0 sec 1.77 GBytes 1.52 Gbits/sec
[ 3] 0.0-10.0 sec 1.82 GBytes 1.56 Gbits/sec
[ 3] 0.0-10.0 sec 1.69 GBytes 1.45 Gbits/sec
Running perf record -a -g ... followed by perf report --no-children
shows:
- 15.72% iperf [kernel.vmlinux] [k] _raw_spin_unlock_irqrestor
- _raw_spin_unlock_irqrestore
- 8.95% arm_smmu_tlb_sync_context
arm_smmu_iotlb_sync
- __iommu_dma_unmap
+ 4.54% iommu_dma_unmap_sg
+ 4.41% iommu_dma_unmap_page
- 2.92% alloc_iova_fast
- iommu_dma_alloc_iova.isra.26
+ 1.54% iommu_dma_map_sg
+ 1.38% __iommu_dma_map
- 2.64% free_iova_fast
iommu_dma_free_iova
- __iommu_dma_unmap
+ 1.35% iommu_dma_unmap_sg
+ 1.29% iommu_dma_unmap_page
which seems to be pointing to the SMMU code as a bottleneck.
Will suggests that his iommu changes (in his for-joerg/arm-smmu/updates
branch), allows IOMMU driver modifications that may have a beneficial
effect. Any thoughts?
Thanks.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next reply other threads:[~2019-09-30 11:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-30 11:00 Russell King - ARM Linux admin [this message]
2019-09-30 11:45 ` SMMU performance Robin Murphy
2019-09-30 11:54 ` Will Deacon
2019-09-30 12:00 ` Robin Murphy
2019-10-02 9:02 ` Will Deacon
2019-10-02 11:09 ` Robin Murphy
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