吞吐问题--3并发io模型

 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
  • close等系统调用时间太长,close都达到20us 

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

 

 

 

 

 

 

 

 

 

但是tcp 协议栈存在spinlock:多个线程相互accept 时,会open一个fd  file-struct存在spinlock也会出现问题,  

 

 

 listener线程负责接受所有的客户端链接

 listener线程每接收到一个新的客户端链接产生一个新的fd,然后通过分发器发送给对应的工作线程(hash方式)

  1.  进行accept处理的listener线程只有一个,在瞬间高并发场景容易成为瓶颈
   2. 一个线程通过IO复用方式处理多个链接fd的数据读写、报文解析及后续业务逻辑处理,这个过程会有严重的排队现象,例如某个链接的报文接收解析完毕后的内部处理时间过长,则其他链接的请求就会阻塞排队 

上述方案经典例子为memcache缓存,适用于内部处理比较快的缓存场景、代理中间场景;但是对更高性能场景, 多线程肯定会触发相关vfs的相关锁,毕竟vfs 部分锁是基于当前进程的不是基于当前线程的

目前对比一下 单listen 和多listen 在多线程下的区别:都是在cps为5w的前提下测试

 

 一个CPU是使用100% 一个是使用30% 明显区别!!

 

posted @ 2021-04-17 15:53  codestacklinuxer  阅读(83)  评论(0编辑  收藏  举报