1. 16 Jun, 2021 3 commits
  2. 15 Jun, 2021 2 commits
    • Hridya Valsaraju's avatar
      dmabuf: Add the capability to expose DMA-BUF stats in sysfs · bdb8d06d
      Hridya Valsaraju authored
      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/+/1549734Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      Signed-off-by: default avatarHridya Valsaraju <hridya@google.com>
      Reported-by: default avatarkernel test robot <lkp@intel.com>
      Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
      Link: https://patchwork.freedesktop.org/patch/msgid/20210603214758.2955251-1-hridya@google.com
      bdb8d06d
    • Ainux's avatar
      drm/ast: Add detect function support · aae74ff9
      Ainux authored
      The existence of the connector cannot be detected,
      so add the detect function to support.
      Signed-off-by: default avatarAinux <ainux.wang@gmail.com>
      Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
      Link: https://patchwork.freedesktop.org/patch/msgid/20210526111515.40015-1-ainux.wang@gmail.com
      aae74ff9
  3. 14 Jun, 2021 7 commits
  4. 12 Jun, 2021 9 commits
  5. 11 Jun, 2021 19 commits