6.内存分配ByteBuf

Reader/writer indexes, heap/direct buffers, slicing, reference counting, and ownership rules.

Allocator abstraction for heap/direct, pooled/unpooled buffers and why allocation strategy is configurable.

Allocator usage, capacity, slicing, copying, reference-count handling, and leak-safe buffer ownership.

Pooled ByteBuf allocation, arenas/chunks/suballocation concepts, reuse benefits, and version-sensitive allocator internals.

Per-thread pooled buffer caching as an allocation optimization, with retention and event-loop affinity trade-offs.