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Date: Tue, 28 Nov 2023 13:33:55 -0800
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: akpm@...ux-foundation.org, alex.williamson@...hat.com,
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Subject: Re: [PATCH 00/16] IOMMU memory observability
On Tue, Nov 28, 2023 at 12:49 PM Pasha Tatashin
<pasha.tatashin@...een.com> wrote:
>
> From: Pasha Tatashin <tatashin@...gle.com>
>
> IOMMU subsystem may contain state that is in gigabytes. Majority of that
> state is iommu page tables. Yet, there is currently, no way to observe
> how much memory is actually used by the iommu subsystem.
>
> This patch series solves this problem by adding both observability to
> all pages that are allocated by IOMMU, and also accountability, so
> admins can limit the amount if via cgroups.
>
> The system-wide observability is using /proc/meminfo:
> SecPageTables: 438176 kB
>
> Contains IOMMU and KVM memory.
>
> Per-node observability:
> /sys/devices/system/node/nodeN/meminfo
> Node N SecPageTables: 422204 kB
>
> Contains IOMMU and KVM memory memory in the given NUMA node.
>
> Per-node IOMMU only observability:
> /sys/devices/system/node/nodeN/vmstat
> nr_iommu_pages 105555
>
> Contains number of pages IOMMU allocated in the given node.
Does it make sense to have a KVM-only entry there as well?
In that case, if SecPageTables in /proc/meminfo is found to be
suspiciously high, it should be easy to tell which component is
contributing most usage through vmstat. I understand that users can do
the subtraction, but we wouldn't want userspace depending on that, in
case a third class of "secondary" page tables emerges that we want to
add to SecPageTables. The in-kernel implementation can do the
subtraction for now if it makes sense though.
>
> Accountability: using sec_pagetables cgroup-v2 memory.stat entry.
>
> With the change, iova_stress[1] stops as limit is reached:
>
> # ./iova_stress
> iova space: 0T free memory: 497G
> iova space: 1T free memory: 495G
> iova space: 2T free memory: 493G
> iova space: 3T free memory: 491G
>
> stops as limit is reached.
>
> This series encorporates suggestions that came from the discussion
> at LPC [2].
>
> [1] https://github.com/soleen/iova_stress
> [2] https://lpc.events/event/17/contributions/1466
>
> Pasha Tatashin (16):
> iommu/vt-d: add wrapper functions for page allocations
> iommu/amd: use page allocation function provided by iommu-pages.h
> iommu/io-pgtable-arm: use page allocation function provided by
> iommu-pages.h
> iommu/io-pgtable-dart: use page allocation function provided by
> iommu-pages.h
> iommu/io-pgtable-arm-v7s: use page allocation function provided by
> iommu-pages.h
> iommu/dma: use page allocation function provided by iommu-pages.h
> iommu/exynos: use page allocation function provided by iommu-pages.h
> iommu/fsl: use page allocation function provided by iommu-pages.h
> iommu/iommufd: use page allocation function provided by iommu-pages.h
> iommu/rockchip: use page allocation function provided by iommu-pages.h
> iommu/sun50i: use page allocation function provided by iommu-pages.h
> iommu/tegra-smmu: use page allocation function provided by
> iommu-pages.h
> iommu: observability of the IOMMU allocations
> iommu: account IOMMU allocated memory
> vhost-vdpa: account iommu allocations
> vfio: account iommu allocations
>
> Documentation/admin-guide/cgroup-v2.rst | 2 +-
> Documentation/filesystems/proc.rst | 4 +-
> drivers/iommu/amd/amd_iommu.h | 8 -
> drivers/iommu/amd/init.c | 91 +++++-----
> drivers/iommu/amd/io_pgtable.c | 13 +-
> drivers/iommu/amd/io_pgtable_v2.c | 20 +-
> drivers/iommu/amd/iommu.c | 13 +-
> drivers/iommu/dma-iommu.c | 8 +-
> drivers/iommu/exynos-iommu.c | 14 +-
> drivers/iommu/fsl_pamu.c | 5 +-
> drivers/iommu/intel/dmar.c | 10 +-
> drivers/iommu/intel/iommu.c | 47 ++---
> drivers/iommu/intel/iommu.h | 2 -
> drivers/iommu/intel/irq_remapping.c | 10 +-
> drivers/iommu/intel/pasid.c | 12 +-
> drivers/iommu/intel/svm.c | 7 +-
> drivers/iommu/io-pgtable-arm-v7s.c | 9 +-
> drivers/iommu/io-pgtable-arm.c | 7 +-
> drivers/iommu/io-pgtable-dart.c | 37 ++--
> drivers/iommu/iommu-pages.h | 231 ++++++++++++++++++++++++
> drivers/iommu/iommufd/iova_bitmap.c | 6 +-
> drivers/iommu/rockchip-iommu.c | 14 +-
> drivers/iommu/sun50i-iommu.c | 7 +-
> drivers/iommu/tegra-smmu.c | 18 +-
> drivers/vfio/vfio_iommu_type1.c | 8 +-
> drivers/vhost/vdpa.c | 3 +-
> include/linux/mmzone.h | 5 +-
> mm/vmstat.c | 3 +
> 28 files changed, 415 insertions(+), 199 deletions(-)
> create mode 100644 drivers/iommu/iommu-pages.h
>
> --
> 2.43.0.rc2.451.g8631bc7472-goog
>
>
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