nodejs 请求接口在高并发下耗时很大，而单个请求非常快

情况： request.js 库请求接口， express.js 做 server ，实现了 curl http://localhost:8080/proxy-api本地一个地址，在 router 里用 request.js 请求接口，统计了一下请求耗时，单个请求耗时很低，如下：

get http://ip:9190/user/getUserInfo 13 ms

然后分别使用 webbench 和 ab 做并发测试，并发 500 ，发现接口有非常大的耗时。

# 测试命令
ab -n 1000 -c 200 -r http://localhost:8080/proxy-api
webbench -t 10 -c 500 http://localhost:8080/proxy-api

# 截取部分响应耗时：
get http://ip:9190/user/getUserInfo 2019 ms
cost time:  2020
get http://ip:9190/user/getUserInfo 2062 ms
cost time:  2062
get http://ip:9190/user/getUserInfo 2064 ms
cost time:  2065
get http://ip:9190/user/getUserInfo 2063 ms
cost time:  2063
get http://ip:9190/user/getUserInfo 2062 ms
cost time:  2063
get http://ip:9190/user/getUserInfo 2063 ms
cost time:  2063
get http://ip:9190/user/getUserInfo 2061 ms
cost time:  2062
get http://ip:9190/user/getUserInfo 2063 ms
cost time:  2064
get http://ip:9190/user/getUserInfo 2063 ms
...
...
get http://ip:9190/user/getUserInfo 1362 ms
cost time:  1362
get http://ip:9190/user/getUserInfo 1361 ms
cost time:  1362
get http://ip:9190/user/getUserInfo 1362 ms
cost time:  1362
get http://ip:9190/user/getUserInfo 1362 ms
cost time:  1362
get http://ip:9190/user/getUserInfo 1362 ms
cost time:  1362
get http://ip:9190/user/getUserInfo 1363 ms
cost time:  1363
get http://ip:9190/user/getUserInfo 1362 ms
cost time:  1362
...
...
get http://ip:9190/user/getUserInfo 1006 ms
cost time:  1006
get http://ip:9190/user/getUserInfo 627 ms
cost time:  628
get http://ip:9190/user/getUserInfo 629 ms
cost time:  629
get http://ip:9190/user/getUserInfo 628 ms
cost time:  629
get http://ip:9190/user/getUserInfo 1403 ms
cost time:  1403
get http://ip:9190/user/getUserInfo 1402 ms

请问哪位朋友有没有解决这类问题的经验？