当TCP分配的内存量超过tcp_mem [1]时，会发生什么？

Question

在man 7 tcp的tcp_mem动作中

说

pressure  When the amount of memory allocated by TCP exceeds
          this number of pages, TCP moderates its memory
          consumption.  This memory pressure state is exited
          once the number of pages allocated falls below the
          low mark.

我想知道TCP如何减轻其内存消耗吗？

TCP会减少套接字的接收或发送缓冲区吗？还是发生了其他事情？