dubbo同步调用很慢

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现在有两个服务A和B分别用docker启动注册到nacos上，A消费队列里的数据然后调用B服务处理，现在的队列消费速度如下：
如果A不调用B，则消费速度能达到和生产速度接近，服务B目前已经注释掉了所有的处理逻辑，因此可以排除业务逻辑影响，dubbo的版本是2.7.8，调用方式为同步调用，线程数配置了500，服务器资源为8核32G，运行时服务器资源充足，dubbo服务调用很慢会是什么问题

No source files or tests are named. Reproduce the Docker-based A/B services with Nacos, Dubbo 2.7.8, synchronous calls, and the reported 500-thread configuration while comparing queue throughput with and without the B call. Done means isolating the cause of the slow invocation and documenting evidence for the fix or configuration change.

Written by the indexing model from the issue text.