brpc server异步response写pb消息耗时较长

Describe the bug (描述bug) brpc server 异步响应模式在往response中写消息字段时，通过前后取时间戳发现，response写pb消息偶现耗时4-5ms，更长时甚至20ms+

response proto格式： { optional uint64 id = 1;
optional int32 stat = 2;
optional uint32 cxxdiali = 3;
repeated uint32 acount = 4; //大概40+个 }

在response赋值pb消息前后取时间戳 // send response long long tik = GetClock(); response->set_id (request->id ()); if (succ) { response->set_stat (STATUS_OK); } else { response->set_stat (STATUS_FAILURE); } response->set_cxxdiali (carty); for (int i = 1; i < size; ++i) { response->add_ acount(xxdialis[i]); } long long tok = GetClock();

当tok-tik 超时3ms以上记录，占比大概2~3/1000： cost: 5 1628476500710->1628476500715. cost: 6 1628476503023->1628476503029. cost: 8 1628476503323->1628476503331. cost: 4 1628476505146->1628476505150. cost: 4 1628476506299->1628476506303. cost: 5 1628476507680->1628476507685. cost: 23 1628476508124->1628476508147. cost: 24 1628476508274->1628476508298. cost: 23 1628476508455->1628476508478. cost: 23 1628476508515->1628476508538. cost: 23 1628476508545->1628476508568. cost: 23 1628476508755->1628476508778. cost: 23 1628476508876->1628476508899. cost: 23 1628476508936->1628476508959. cost: 23 1628476509056->1628476509079.

To Reproduce (复现方法)

Expected behavior (期望行为)

Versions (各种版本) OS: linux 3.10.0-514.44.5.10.h254.x86_64 Compiler： gcc 9.x brpc: 0.9.7 protobuf: 3.6.1

Additional context/screenshots (更多上下文/截图)

我的服务占用内存很高，我判断是pb在写消息时申请内存导致的偶现延时增大，请问各位是否有什么优化建议？我查了pb的资料有arena方式创建message，不知道brpc内是否支持，如何调用？或者各位大佬有其他好的建议？

多谢！