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Overview ======== The patch adds DMA-BUF statistics to /sys/kernel/dmabuf/buffers. It allows statistics to be enabled for each DMA-BUF in sysfs by enabling the config CONFIG_DMABUF_SYSFS_STATS. The following stats will be exposed by the interface: /sys/kernel/dmabuf/buffers/<inode_number>/exporter_name /sys/kernel/dmabuf/buffers/<inode_number>/size /sys/kernel/dmabuf/buffers/<inode_number>/attachments/<attach_uid>/device /sys/kernel/dmabuf/buffers/<inode_number>/attachments/<attach_uid>/map_counter The inode_number is unique for each DMA-BUF and was added earlier [1] in order to allow userspace to track DMA-BUF usage across different processes. Use Cases ========= The interface provides a way to gather DMA-BUF per-buffer statistics from production devices. These statistics will be used to derive DMA-BUF per-exporter stats and per-device usage stats for Android Bug reports. The corresponding userspace changes can be found at [2]. Telemetry tools will also capture this information(along with other memory metrics) periodically as well as on important events like a foreground app kill (which might have been triggered by Low Memory Killer). It will also contribute to provide a snapshot of the system memory usage on other events such as OOM kills and Application Not Responding events. Background ========== Currently, there are two existing interfaces that provide information about DMA-BUFs. 1) /sys/kernel/debug/dma_buf/bufinfo debugfs is however unsuitable to be mounted in production systems and cannot be considered as an alternative to the sysfs interface being proposed. 2) proc/<pid>/fdinfo/<fd> The proc/<pid>/fdinfo/<fd> files expose information about DMA-BUF fds. However, the existing procfs interfaces can only provide information about the buffers for which processes hold fds or have the buffers mmapped into their address space. Since the procfs interfaces alone cannot provide a full picture of all DMA-BUFs in the system, there is the need for an alternate interface to provide this information on production systems. The patch contains the following major improvements over v1: 1) Each attachment is represented by its own directory to allow creating a symlink to the importing device and to also provide room for future expansion. 2) The number of distinct mappings of each attachment is exposed in a separate file. 3) The per-buffer statistics are now in /sys/kernel/dmabuf/buffers inorder to make the interface expandable in future. All of the improvements above are based on suggestions/feedback from Daniel Vetter and Christian König. A shell script that can be run on a classic Linux environment to read out the DMA-BUF statistics can be found at [3](suggested by John Stultz). [1]: https://lore.kernel.org/patchwork/patch/1088791/ [2]: https://android-review.googlesource.com/q/topic:%22dmabuf-sysfs%22+(status:open%20OR%20status:merged) [3]: https://android-review.googlesource.com/c/platform/system/memory/libmeminfo/+/1549734 Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Hridya Valsaraju <hridya@google.com> Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20210603214758.2955251-1-hridya@google.com
89 lines
2.9 KiB
Plaintext
89 lines
2.9 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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menu "DMABUF options"
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config SYNC_FILE
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bool "Explicit Synchronization Framework"
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default n
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select DMA_SHARED_BUFFER
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help
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The Sync File Framework adds explicit synchronization via
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userspace. It enables send/receive 'struct dma_fence' objects to/from
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userspace via Sync File fds for synchronization between drivers via
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userspace components. It has been ported from Android.
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The first and main user for this is graphics in which a fence is
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associated with a buffer. When a job is submitted to the GPU a fence
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is attached to the buffer and is transferred via userspace, using Sync
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Files fds, to the DRM driver for example. More details at
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Documentation/driver-api/sync_file.rst.
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config SW_SYNC
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bool "Sync File Validation Framework"
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default n
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depends on SYNC_FILE
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depends on DEBUG_FS
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help
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A sync object driver that uses a 32bit counter to coordinate
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synchronization. Useful when there is no hardware primitive backing
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the synchronization.
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WARNING: improper use of this can result in deadlocking kernel
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drivers from userspace. Intended for test and debug only.
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config UDMABUF
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bool "userspace dmabuf misc driver"
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default n
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depends on DMA_SHARED_BUFFER
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depends on MEMFD_CREATE || COMPILE_TEST
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help
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A driver to let userspace turn memfd regions into dma-bufs.
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Qemu can use this to create host dmabufs for guest framebuffers.
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config DMABUF_MOVE_NOTIFY
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bool "Move notify between drivers (EXPERIMENTAL)"
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default n
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help
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Don't pin buffers if the dynamic DMA-buf interface is available on
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both the exporter as well as the importer. This fixes a security
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problem where userspace is able to pin unrestricted amounts of memory
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through DMA-buf.
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This is marked experimental because we don't yet have a consistent
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execution context and memory management between drivers.
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config DMABUF_DEBUG
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bool "DMA-BUF debug checks"
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default y if DMA_API_DEBUG
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help
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This option enables additional checks for DMA-BUF importers and
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exporters. Specifically it validates that importers do not peek at the
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underlying struct page when they import a buffer.
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config DMABUF_SELFTESTS
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tristate "Selftests for the dma-buf interfaces"
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default n
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depends on DMA_SHARED_BUFFER
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menuconfig DMABUF_HEAPS
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bool "DMA-BUF Userland Memory Heaps"
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select DMA_SHARED_BUFFER
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help
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Choose this option to enable the DMA-BUF userland memory heaps.
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This options creates per heap chardevs in /dev/dma_heap/ which
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allows userspace to allocate dma-bufs that can be shared
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between drivers.
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menuconfig DMABUF_SYSFS_STATS
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bool "DMA-BUF sysfs statistics"
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select DMA_SHARED_BUFFER
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help
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Choose this option to enable DMA-BUF sysfs statistics
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in location /sys/kernel/dmabuf/buffers.
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/sys/kernel/dmabuf/buffers/<inode_number> will contain
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statistics for the DMA-BUF with the unique inode number
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<inode_number>.
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source "drivers/dma-buf/heaps/Kconfig"
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endmenu
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