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.