为什么boost :: asio :: async_write需要这么多时间？

Question

我使用boost :: asio处理我的异步tcp请求，但是我发现每次调用boost :: asio :: async_write都需要数百微秒。我认为这只是将数据放入TCP发送缓冲区。为什么这么久？谢谢大家！

==== 227 do_write_impl
 ==== 274 do_write_impl
 ==== 238 do_write_impl
 ==== 60 do_write_impl
 ==== 220 do_write_impl
 ==== 229 do_write_impl
 ==== 368 do_write_impl
 ==== 189 do_write_impl
 ==== 221 do_write_impl
 ==== 234 do_write_impl
 

       auto b = boost::asio::buffer(msg_send->get_header(), length);
       auto f = [self, this] (const bsys::error_code& e, std::size_t bytes_trans) { handle_write_impl(e, bytes_trans); };

       struct timeval tv1 {0, 0}; 
       struct timeval tv2 {0, 0}; 
       gettimeofday(&tv1, nullptr); const auto beg = tv1.tv_sec * 1000000 + tv1.tv_usec;

       boost::asio::async_write(socket_,
               b,                      
               f   
               );  

       gettimeofday(&tv2, nullptr); const auto end = tv2.tv_sec * 1000000 + tv2.tv_usec;
       std::cout << " ==== " << (end - beg) << " do_write_impl " << std::endl;