Allocation groups also help to optimize parallel IO performance on multiprocessor systems, because more than one metadata update can be "in transit" at the same time.
分配组还有助于在多处理器系统上优化并行io性能，因为可以同时有多个元数据更新处于“在传输中”。
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All of these optimizations are to aid in higher performance, and are generally transparent to the user, but on multiprocessor systems, these complexities may sometimes show through.
However, if your application is deployed on a multiprocessor system or USES a very large heap, you may get some performance boost from changing collector options.