kc3-lang/angle/src/libANGLE/renderer/vulkan/doc/Allocators.md

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• Hash : 684ff60b
  Author :
  Date : 2022-06-21T10:52:31
  

  Vulkan: Add shared ring buffer cmd alloc feature
  
  * Added RingBufferAllocator.cpp with implementation.
    * Main classes:
      * RingBufferAllocator (fast allocation with bulk deallocation)
      * SharedRingBufferAllocator (wrapper to help with shared use and
      multiple threads)
  
  * Implemented "angle_enable_vulkan_shared_ring_buffer_cmd_alloc"
  feature. (Disabled by default)
    * Details (from the original CL)
      * The angle::PoolAllocator replaced with
      angle::RingBufferAllocator.
  
      * Before, there was separate angle::PoolAllocator per each
      CommandBufferHelper. Now, a single angle::RingBufferAllocator
      is shared between multiple CommandBufferHelper objects.
  
      * Commands data from multiple CommandBufferHelpers is
      tightly packed without fragmentation.
  
    * Significantly less memory overhead, observed with enabled
      async queue.
  
  * Moved the parts of the code related to the allocators into the
    classes in the new AllocatorHelperPool and AllocatorHelperRing files
    for better management. The allocator can be switched by changing the
    following BUILD flag:
    `angle_enable_vulkan_shared_ring_buffer_cmd_alloc`
  
      * It is connected to the following macro:
        ANGLE_ENABLE_VULKAN_SHARED_RING_BUFFER_CMD_ALLOC
  
    * The two main allocator classes in each file are aliased as:
      * SecondaryCommandBlockAllocator (in CommandBufferHelper objects)
      * SecondaryCommandBlockPool (in SecondaryCommandBuffer)
  
    * Also added placeholder functions for VulkanSecondaryCommandBuffer.
  
  * Added descriptions regarding the two allocators.
    * renderer/vulkan/doc/Allocators.md
  
  Credit: Original CL authored by Igor Nazarov <i.nazarov@samsung.com>
  
  Bug: angleproject:6401
  Bug: b/256666069
  Change-Id: I0f24793eef6334bf4ff8e327b9665338807dad37
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3715968
  Reviewed-by: Charlie Lao <cclao@google.com>
  Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
  Commit-Queue: Amirali Abdolrashidi <abdolrashidi@google.com>
  

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---

Source

• src/libANGLE/renderer/vulkan/doc/Allocators.md

• # Allocators
  
  Allocator helpers are used in the command buffer objects as a means to allocate memory for the
  latter. Regardless of the inner workings of the allocation method they use, they use the same
  interface in the ANGLE code.
  
  ## Allocator types
  
  There are currently two types of allocators defined in ANGLE:
  
  * Pool allocators; and
  
  * Ring buffer allocators.
  
  **ANGLE uses pool allocators by default.** To switch to ring buffer allocators, the flag
  `angle_enable_vulkan_shared_ring_buffer_cmd_alloc` should be enabled in GN args. This flag appears
  as `ANGLE_ENABLE_VULKAN_SHARED_RING_BUFFER_CMD_ALLOC` in the code, which is used to select the
  allocator type.
  
  ### Common interface
  
  In `SecondaryCommandBuffer.h`, the helper classes related to the selected allocator type are
  aliased as the following:
  
  * `SecondaryCommandMemoryAllocator`
  
    * This is the main allocator object used in the allocator helper classes. It is used as a type
  	for some of the allocator helpers' public functions.
  
  * `SecondaryCommandBlockPool`
  
    * This allocator is used in `SecondaryCommandBuffer`.
  
  * `SecondaryCommandBlockAllocator`
  
    * This allocator is defined in `CommandBufferHelperCommon`, and by extension, is used in its
  	derived helper classes for render pass and outside render pass command buffer helpers.
  
  
  ### Pool allocator helpers
  
  _Files: `AllocatorHelperPool.cpp` and `AllocatorHelperPool.h`_
  
  - `SecondaryCommandMemoryAllocator` -> `DedicatedCommandMemoryAllocator` -> `angle::PoolAllocator`
  
  - `SecondaryCommandBlockPool` -> `DedicatedCommandBlockPool`
  
  - `SecondaryCommandBlockAllocator` -> `DedicatedCommandBlockAllocator`
  
  #### Notes
  
  * `attachAllocator()` and `detachAllocator()` functions are no-ops for the pool allocators.
  
  * Regarding `SecondaryCommandBlockAllocator` in pool allocators:
  
    * `init()` works only with pool allocators.
  
    * `hasAllocatorLinks()` always returns `false`.
  
    * `terminateLastCommandBlock()` is no-op.
  
  ### Ring buffer allocator helpers
  
  _Files: `AllocatorHelperRing.cpp` and `AllocatorHelperRing.h`_
  
  - `SecondaryCommandMemoryAllocator` -> `SharedCommandMemoryAllocator` -> `angle::SharedRingBufferAllocator`
  
  - `SecondaryCommandBlockPool` -> `SharedCommandBlockPool`
  
  - `SecondaryCommandBlockAllocator` -> `SharedCommandBlockAllocator`
  
  #### Notes
  
  * It can be seen that in the context's initialization and destruction, and flushing the command
    processor's commands, there are calls to attach and detach an allocator (via `attachAllocator()`
    and `detachAllocator()`). Please note that **these functions are only defined for ring buffer
    allocators**.
  
  * Regarding `SecondaryCommandBlockAllocator` in ring buffer allocators:
  
    * `init()` is no-op.
  
    * `hasAllocatorLinks()` checks the allocator and the shared checkpoint.
  
    * `terminateLastCommandBlock()` is only used in ring buffer allocators.
  

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