Proposal to report GPU private memory allocations with sysfs nodes

[Yiwei Zhang]

Hi folks,

This is Yiwei from the Android Platform Graphics team. On the downstream
Android, vendors used to report GPU private memory allocations with debugfs
nodes in their own formats. However, debugfs nodes are getting deprecated
in the next Android release, so we are taking the chance to unify all the
vendors to migrate their existing debugfs nodes into a standardized sysfs
node structure. Then the platform is able to do a bunch of useful
things: memory profiling, system health coverage, field metrics, local
shell dump, in-app api, etc.

Some vendors tend to do a lot of upstreams, so we are also seeking the
upstream possibilities here instead of making it an Android only thing.

Attached are screenshots for the node structure we drafted and an example
for that.

For the top level root, vendors can choose their own names based on the
value of ro.gfx.sysfs.0 the vendors set.

   - For the multiple gpu driver cases, we can use ro.gfx.sysfs.1,
   ro.gfx.sysfs.2 for the 2nd and 3rd KMDs.
   - It's also allowed to put some sub-dir for example "kgsl/gpu_mem" or
   "mali0/gpu_mem" in the ro.gfx.sysfs.<channel> property if the root name
   under /sys/devices/ is already created and used for other purposes.


For the 2nd level pids, there are usually just a couple of them per
snapshot, since we only takes snapshot for the active ones.

For the 3rd level types, the type name will be one of the GPU memory object
types in lower case, and the value will be a comma separated sequence of
size values for all the allocations under that specific type.

   - For the GPU memory object types, we defined 9 different types for
   Android:
      -     // not accounted for in any other category
          UNKNOWN = 0;
          // shader binaries
          SHADER = 1;
          // allocations which have a lifetime similar to a VkCommandBuffer
          COMMAND = 2;
          // backing for VkDeviceMemory
          VULKAN = 3;
          // GL Texture and RenderBuffer
          GL_TEXTURE = 4;
          // GL Buffer
          GL_BUFFER = 5;
          // backing for query
          QUERY = 6;
          // allocations which have a lifetime similar to a VkDescriptorSet
          DESCRIPTOR = 7;
          // random transient things that the driver needs
          TRANSIENT = 8;
      - We are wondering if those type enumerations make sense to the
      upstream side as well, or maybe we just deal with our own different type
      sets. Cuz on the Android side, we'll just read those nodes named
after the
      types we defined in the sysfs node structure.
   - The node value can be: 4096,81920,...,4096


Looking forward to any concerns/comments/suggestions!

Best regards,
Yiwei
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