Explore a roundtable discussion on ION / dma-buf allocators and constraint solving featuring key Android developers and upstream community members. Delve into topics such as centralized vs device-specific allocators, userland device constraint discovery, and attach time in-kernel constraint solving. Learn about potential extensions to iommu/dma-api, convenience APIs, ION vs dmabuf comparisons, and internal API structures. Examine slow path fallbacks, control over user space, hot plug devices, and partitioning constraints. Investigate chunk heap types, page migration techniques, heap allocation strategies, and asymmetric memory considerations. Discover IOU heaps, their interfaces, and preferences, as well as system tuning approaches, dma mapping, permissions, and usage flags. Gain insights into the complexities of ION heaps and their implications for userspace development in this comprehensive 48-minute session from the Linux Plumbers Conference.