docs: update README.md

README-zh.md

@@ -155,6 +155,8 @@ rathole 的延迟与 [frp](https://github.com/fatedier/frp) 相近，在高并
 
 关于测试进行的更多细节，参见单独页面 [Benchmark](./docs/benchmark.md)。
 
+**但是，不要从这里得出结论，`rathole` 能让内网转发出来的服务快上数倍。** Benchmark 是在本地回环上进行的，其结果说明了任务受 CPU 限制时的结果。当用户的网络不是瓶颈时，用户能得到很大的提升。但是，对很多用户来说并不是这样。在这种情况下，`rathole` 能带来的主要好处是更少的资源占用，带宽和延迟不一定有显著的改善。
+
 ![http_throughput](./docs/img/http_throughput.svg)
 ![tcp_bitrate](./docs/img/tcp_bitrate.svg)
 ![udp_bitrate](./docs/img/udp_bitrate.svg)

README.md

@@ -153,6 +153,8 @@ rathole has similar latency to [frp](https://github.com/fatedier/frp), but can h
 
 For more details, see the separate page [Benchmark](./docs/benchmark.md).
 
+**However, don't take it from here that `rathole` can magically make your forwarded service faster several times than before.** The benchmark is done on local loopback, indicating the performance when the task is cpu-bounded. One can gain quite a improvement if the network is not the bottleneck. Unfortunately, that's not true for many users. In that case, the main benefit is lower resource consumption, and the bandwidth and the latency may not improved significantly.
+
 ![http_throughput](./docs/img/http_throughput.svg)
 ![tcp_bitrate](./docs/img/tcp_bitrate.svg)
 ![udp_bitrate](./docs/img/udp_bitrate.svg)