Go 性能与GOMAXPROCS的关系

起初是看到一篇文章《[容器中某Go服务GC停顿经常超过100ms排查][(https://mp.weixin.qq.com/s/Lk1EbiT7WprVOyX_dXYMyg)》，里面提到了容器内 GOMAXPROCS 取值为宿主机，使得容器 内 P 数量增大，增加了 GC 压力，造成压测时 T99很高。正好最近压测也在为这个问题头疼，就按照文章里的内容做了实验。结果半路发现了一些不完全一致的结果，觉得挺有意思就记录一下。

实验器材：

机器：mac mini 2012 later 387 4c/12g 系统：Linux unas-mini 4.9.0-11-amd64 #1 SMP Debian 4.9.189-3 (2019-09-02) x86_64 GNU/Linux Go环境：docker 17.12.0-ce golang1.10.3 / golang1.13.3 容器限制：512m 2c 压测环境：家庭局域网，本机到被压机 ping 2ms

程序模板（编译三个版本，GOMAXPROCS 分别为 2、4、32）

package main

func GetStatus(w http.ResponseWriter, _ *http.Request) {
	b := Response{Status: "idle", Data: 32 }
	json.NewEncoder(w).Encode(b)
}

func main() {
	runtime.GOMAXPROCS(4)

	router := mux.NewRouter()
	router.HandleFunc("/status", GetStatus).Methods("GET")
	log.Fatal(http.ListenAndServe(":8123", router))
}

首先用非常小的流量做个测试

wrk -t2 -c4 -d30s --latency http://192.168.10.24:32778/status

​

wrk -t4 -c8 -d30s --latency http://192.168.10.24:32778/status

GOMAXPROCS=2

  4 threads and 8 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     2.06ms    2.22ms  59.27ms   97.29%
    Req/Sec     1.09k   173.04     1.27k    92.33%
  Latency Distribution
     50%    1.71ms
     75%    1.95ms
     90%    2.40ms
     99%   11.51ms
  130308 requests in 30.05s, 17.90MB read
Requests/sec:   4336.24
Transfer/sec:    609.78KB

GOMAXPROCS=4

  4 threads and 8 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     3.79ms   17.93ms 355.91ms   98.43%
    Req/Sec     1.06k   201.50     1.29k    87.58%
  Latency Distribution
     50%    1.71ms
     75%    2.04ms
     90%    2.71ms
     99%   39.86ms
  125557 requests in 30.08s, 17.36MB read
Requests/sec:   4174.79
Transfer/sec:    591.16KB

  4 threads and 8 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     1.98ms    2.20ms  56.15ms   97.80%
    Req/Sec     1.10k   122.68     1.29k    83.50%
  Latency Distribution
     50%    1.69ms
     75%    1.95ms
     90%    2.36ms
     99%    6.87ms
  131746 requests in 30.05s, 18.22MB read
Requests/sec:   4384.52
Transfer/sec:    620.85KB

GOMAXPROCS=32