[RFC PATCH v2 00/19] Try to reduce lock contention on the SMMUv3 command queue

From: Will Deacon <will@kernel.org>
To: iommu@lists.linux-foundation.org
Cc: Vijay Kilary <vkilari@codeaurora.org>,
	Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
	Will Deacon <will@kernel.org>, Jan Glauber <jglauber@marvell.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Jayachandran Chandrasekharan Nair <jnair@marvell.com>,
	Jon Masters <jcm@redhat.com>, Robin Murphy <robin.murphy@arm.com>
Subject: [RFC PATCH v2 00/19] Try to reduce lock contention on the SMMUv3 command queue
Date: Thu, 11 Jul 2019 18:19:08 +0100	[thread overview]
Message-ID: <20190711171927.28803-1-will@kernel.org> (raw)

Hi everyone,

This is a significant rework of the RFC I previously posted here:

  https://lkml.kernel.org/r/20190611134603.4253-1-will.deacon@arm.com

But this time, it looks like it might actually be worthwhile according
to my perf profiles, where __iommu_unmap() falls a long way down the
profile for a multi-threaded netperf run. I'm still relying on others to
confirm this is useful, however.

Some of the changes since last time are:

  * Support for constructing and submitting a list of commands in the
    driver

  * Numerous changes to the IOMMU and io-pgtable APIs so that we can
    submit commands in batches

  * Removal of cmpxchg() from cmdq_shared_lock() fast-path

  * Code restructuring and cleanups

This current applies against my iommu/devel branch that Joerg has pulled
for 5.3. If you want to test it out, I've put everything here:

  https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=iommu/cmdq

Feedback welcome. I appreciate that we're in the merge window, but I
wanted to get this on the list for people to look at as an RFC.

Cheers,

Will

--->8

Cc: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
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>

Will Deacon (19):
  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()
  iommu/arm-smmu-v3: Separate s/w and h/w views of prod and cons indexes
  iommu/arm-smmu-v3: Drop unused 'q' argument from Q_OVF macro
  iommu/arm-smmu-v3: Move low-level queue fields out of arm_smmu_queue
  iommu/arm-smmu-v3: Operate directly on low-level queue where possible
  iommu/arm-smmu-v3: Reduce contention during command-queue insertion
  iommu/arm-smmu-v3: Defer TLB invalidation until ->iotlb_sync()

 drivers/gpu/drm/panfrost/panfrost_mmu.c |  24 +-
 drivers/iommu/amd_iommu.c               |  11 +-
 drivers/iommu/arm-smmu-v3.c             | 856 ++++++++++++++++++++++++--------
 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/vfio/vfio_iommu_type1.c         |  27 +-
 include/linux/io-pgtable.h              |  57 ++-
 include/linux/iommu.h                   |  92 +++-
 23 files changed, 1090 insertions(+), 407 deletions(-)

-- 
2.11.0

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