[Impeller] Maintain a global map of each context's currently active thread-local command pools #169548
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…hread-local command pools The Impeller Vulkan back end creates a thread-local map of contexts to CommandPoolVK instances for each thread that uses Vulkan. This allows a thread to obtain the CommandPoolVK that is currently in use for a given context. When a context is shut down, the Vulkan resources used by each thread's local CommandPoolVK for that context must be freed. To do this, CommandPoolVK maintains a global map of CommandPoolVK instances. Prior to this PR Impeller was appending to the context's pool list in the global map each time a new CommandPoolVK was created. In the original implementation this worked because Impeller was only creating one CommandPoolVK per thread for a given context. However, CommandPoolVK later adopted a recycling scheme where each frame creates a new CommandPoolVK instance that acquires a Vulkan command pool from the CommandPoolRecyclerVK. So inserting every CommandPoolVK into the global map will cause the global map to grow unbounded. This PR changes the structure of the global map. The global map will now associate each context with a map of thread IDs to the CommandPoolVK that is currently placed in the thread's local storage. When a thread calls CommandPoolRecyclerVK::Dispose to clear its thread-local CommandPoolVK for a context, the corresponding entry is also removed from the global map. Fixes flutter#169208
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… playground tests On Vulkan the golden tests are using a single ContextVK instance that is shared among all tests. The ContextVK is never deleted by the test harness. So when the test process exits there may still be a CommandPoolVK in the thread-local map. The map and the CommandPoolVK will then be destructed when global and thread-local objects are destructed, which may be unsafe. Calling DisposeThreadLocalCachedResources forces cleanup of the thread-local map when each test case finishes.
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…hread-local command pools (flutter#169548) The Impeller Vulkan back end creates a thread-local map of contexts to CommandPoolVK instances for each thread that uses Vulkan. This allows a thread to obtain the CommandPoolVK that is currently in use for a given context. When a context is shut down, the Vulkan resources used by each thread's local CommandPoolVK for that context must be freed. To do this, CommandPoolVK maintains a global map of CommandPoolVK instances. Prior to this PR Impeller was appending to the context's pool list in the global map each time a new CommandPoolVK was created. In the original implementation this worked because Impeller was only creating one CommandPoolVK per thread for a given context. However, CommandPoolVK later adopted a recycling scheme where each frame creates a new CommandPoolVK instance that acquires a Vulkan command pool from the CommandPoolRecyclerVK. So inserting every CommandPoolVK into the global map will cause the global map to grow unbounded. This PR changes the structure of the global map. The global map will now associate each context with a map of thread IDs to the CommandPoolVK that is currently placed in the thread's local storage. When a thread calls CommandPoolRecyclerVK::Dispose to clear its thread-local CommandPoolVK for a context, the corresponding entry is also removed from the global map. Fixes flutter#169208
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The Impeller Vulkan back end creates a thread-local map of contexts to CommandPoolVK instances for each thread that uses Vulkan. This allows a thread to obtain the CommandPoolVK that is currently in use for a given context.
When a context is shut down, the Vulkan resources used by each thread's local CommandPoolVK for that context must be freed. To do this, CommandPoolVK maintains a global map of CommandPoolVK instances.
Prior to this PR Impeller was appending to the context's pool list in the global map each time a new CommandPoolVK was created. In the original implementation this worked because Impeller was only creating one CommandPoolVK per thread for a given context.
However, CommandPoolVK later adopted a recycling scheme where each frame creates a new CommandPoolVK instance that acquires a Vulkan command pool from the CommandPoolRecyclerVK. So inserting every CommandPoolVK into the global map will cause the global map to grow unbounded.
This PR changes the structure of the global map. The global map will now associate each context with a map of thread IDs to the CommandPoolVK that is currently placed in the thread's local storage. When a thread calls CommandPoolRecyclerVK::Dispose to clear its thread-local CommandPoolVK for a context, the corresponding entry is also removed from the global map.
Fixes #169208