性能测试分析之CPU篇

1、性能测试分析之cpu篇目录u linux系统结构简介u 用户态cpu消耗分析u 内核态cpu消耗分析u 硬中断&软中断u load average剖析linux系统结构linux系统结构几种cpu消耗us%user cpu time (or) % cpu time spent in user spacesy%system cpu time (or) % cpu time spent in kernel spaceni%user nice cpu time (or) % cpu time spent on low priority processesid%idle cpu time (or) %

2、 cpu time spent idlewa%io wait cpu time (or) % cpu time spent in wait (on disk)hi%hardware irq (or) % cpu time spent servicing/handling hardware interruptssi%software irq (or) % cpu time spent servicing/handling software interruptsst%steal time - - % cpu time in involuntary wait by virtual cpu while

3、 hypervisor is servicing another processor (or) % cpu time stolen from a virtual machinecpu调度用户态cpu例1：程序cpu usr%瓶颈问题定位。模拟程序testmap主线程：死循环阻塞线程1： sleep线程2 : 循环map find操作执行命令：top h p 7152用户态cpu执行命令：pstack 7152分析过程：通过top h p xx 发现线程7153占用cpu特别高1. 通过pstack 发现线程7153在做map查询操作，大量的红黑树查找操作。用户态cpu例2：程序cpu usr%

4、瓶颈问题定位。（如果线程cpu消耗比较均衡）执行：perf top -p 7152 -e cycles:u参考案例：vtdu因cpu消耗过高回滚内核态cpu例3：定位sy%消耗过高问题执行：perf top -p xxxx -e cycles:k内核态cpu上下文切换（只会发生在内核态）当前执行任务时间片用完，cpu正常调度下一个任务。i/o阻塞抢占锁资源，用户代码挂起（sleep）,等待条件变量1. 硬中断&软中断例4：程序问题造成大量的上下文切换执行：testcsw程序开启100个线程，每个线程usleep（1*1000）硬中断&软中断网卡中断为例：频繁的数据包收发会耗尽cpu时间多核cp

5、u，如何做中断负载均衡？多队列网卡： 只需配置每个队列的cpu亲和性，smp_affinity。单队列网卡： 先通过rps模拟出多队列再最cpu亲和性。rps：根据数据包源地址、目的地址和源端口做hash，来选择不同cpu。rfs： rps负载均衡的优化。load average剖析load averagesystem load averages is the average number of processes that are either in a runablerunable or uninterruptableuninterruptable state. a process in

6、a runnable state is either using the cpu or waiting to use the cpu. a process inuninterruptable state is waiting for some i/o access,egwaiting for disk. the averages are taken over the three time intervals. load averages are not normalized for the number of cpus in a system, so a loadaverage of 1 means a single cpu system is loaded all the time while on a 4 cpu system it means it was idle 75% of the time.进程状态load average剖析例5：task_uninterruptible状态进程过