吞吐问题--3

 开始优化应用层！！

目前可以看出问题如下：

• select 耗时太多！！！！
•  read  系统调用的errors次数占比13% 这是一个问题
• read的次数太多，是不是可以调大接收缓存减少read 次数，同时使用zero_copy  tcp  ： A reworked TCP zero-copy receive API
  
• write 次数比read 还多，应该可以使用聚合接口
• socket bind ioctl 使用了3178次，那么client  server fd 为 3178*2=6356  及时使用setsockopt 设置TCP_NODELAY 、SO_REUSEADDR、
  SO_RCVBUF/SO_SNDBUF 、SO_KEEPALIVE  、SO_REUSEPORT、TCP_DEFER_ACCEPT 、SO_LINGER等 但是次数不至于达到27.8w次
• epoll_ctl比较频繁 远大于3178 目前为5.2w
• recvfrom 失败出错率较高50%
• 使用close 后继续使用shuwdown 通shutdown 出错率大约为50%
• futex 有必要吗？
• restart_syscall 太耗时

当前模型：

 明显存在竞争资源瓶颈

使用如下模型测试一下：

结果为：

perf stat -p 9880  sleep 10

 Performance counter stats for process id '9880':

      30372.082735 task-clock-msecs         #      3.037 CPUs 
            340714 context-switches         #      0.011 M/sec
               288 CPU-migrations           #      0.000 M/sec
               150 page-faults              #      0.000 M/sec
       65299950534 cycles                   #   2149.999 M/sec  (scaled from 66.24%)
       12797366330 instructions             #      0.196 IPC    (scaled from 83.37%)
        3284418549 branches                 #    108.139 M/sec  (scaled from 83.17%)
          15383662 branch-misses            #      0.468 %      (scaled from 83.69%)
         195263517 cache-references         #      6.429 M/sec  (scaled from 83.42%)
          29353131 cache-misses             #      0.966 M/sec  (scaled from 83.49%)

       10.000647442  seconds time elapsed

perf stat -p 9880  sleep 10

 Performance counter stats for process id '9880':

      30754.416664 task-clock-msecs         #      3.075 CPUs 
            341624 context-switches         #      0.011 M/sec
               358 CPU-migrations           #      0.000 M/sec
               121 page-faults              #      0.000 M/sec
       66197865785 cycles                   #   2152.467 M/sec  (scaled from 66.21%)
       12878834358 instructions             #      0.195 IPC    (scaled from 83.57%)
        3319059775 branches                 #    107.921 M/sec  (scaled from 83.42%)
          15481326 branch-misses            #      0.466 %      (scaled from 83.72%)
         194900683 cache-references         #      6.337 M/sec  (scaled from 83.63%)
          28394751 cache-misses             #      0.923 M/sec  (scaled from 83.03%)

       10.001158953  seconds time elapsed

虽然解决了惊群以及多线程抢占 listen fd 问题

对比以前的stat结果：

perf  stat -p 9884 sleep 10 

 Performance counter stats for process id '9884':

     200815.127256 task-clock-msecs         #     20.075 CPUs 
           2456764 context-switches         #      0.012 M/sec
              1294 CPU-migrations           #      0.000 M/sec
              3583 page-faults              #      0.000 M/sec
      430791607582 cycles                   #   2145.215 M/sec  (scaled from 66.57%)
       63233677155 instructions             #      0.147 IPC    (scaled from 83.19%)
       18174748495 branches                 #     90.505 M/sec  (scaled from 83.19%)
          70154714 branch-misses            #      0.386 %      (scaled from 83.45%)
         806455643 cache-references         #      4.016 M/sec  (scaled from 83.36%)
         164527072 cache-misses             #      0.819 M/sec  (scaled from 83.44%)

       10.003181505  seconds time elapsed

perf  stat -p 9884 sleep 10 

 Performance counter stats for process id '9884':

     203748.965387 task-clock-msecs         #     20.373 CPUs 
           2274598 context-switches         #      0.011 M/sec
              1768 CPU-migrations           #      0.000 M/sec
              3570 page-faults              #      0.000 M/sec
      438541182863 cycles                   #   2152.360 M/sec  (scaled from 66.80%)
       63421130555 instructions             #      0.145 IPC    (scaled from 83.34%)
       18428625598 branches                 #     90.448 M/sec  (scaled from 83.23%)
          69229085 branch-misses            #      0.376 %      (scaled from 83.41%)
         770039314 cache-references         #      3.779 M/sec  (scaled from 83.14%)
         158705951 cache-misses             #      0.779 M/sec  (scaled from 83.48%)

       10.000827457  seconds time elapsed

 使用perf stat 统计 分析：目前这种改动有一定提升；同时 cps 大约为6w

对于网络架构：目前认为可以做出如下考虑