Linux实时性能测试工具之cyclictest使用详解

cyclictest 是 Linux 系统中 rt-tests 下的用于测试内核实时性能的常用工具，通过创建高精度定时线程并测量其唤醒延迟，评估系统的中断响应、调度延迟等实时特性。

cyclictest 安装

下面是 cyclictest 的安装方法，供参考：

# 下载cyclictest原码git clone git://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git# 切换branch stable/v1.0git checkout stable/v1.0# 编译make

cyclictest 计算延时原理

cyclictest计算延时的原理是通过记录进程睡眠的开始时间、实际睡眠时间以及真正唤醒并运行的时间，用实际唤醒时间减去实际睡眠时间和睡眠开始时间来得出延时。

• 程序会记录进程睡眠的开始时间 t1
• 进程实际睡眠时间 t2
• 进程 真正唤醒并运行的时间为 t3
• 延时结果即为 t3 - t2 - t1

cyclictest 运行

编译完成后可以在运行cyclictest， 例如：

sudo ./cyclictest -m -n -p95 -d0 -a 1-17 -t 17

查看参数可以使用：

./cyclictest -h./cyclictest: option requires an argument -- 'h'cyclictest V 1.00Usage:cyclictest <options>-a [CPUSET] --affinity     Run thread #N on processor #N, if possible, or if CPUSET                           given, pin threads to that set of processors in round-                           robin order.  E.g. -a 2 pins all threads to CPU 2,                           but -a 3-5,0 -t 5 will run the first and fifth                           threads on CPU (0),thread #2 on CPU 3, thread #3                           on CPU 4, and thread #5 on CPU 5.-A USEC  --aligned=USEC    align thread wakeups to a specific offset-b USEC  --breaktrace=USEC send break trace command when latency > USEC-B       --preemptirqs     both preempt and irqsoff tracing (used with -b)-c CLOCK --clock=CLOCK     select clock                           0 = CLOCK_MONOTONIC (default)                           1 = CLOCK_REALTIME-C       --context         context switch tracing (used with -b)-d DIST  --distance=DIST   distance of thread intervals in us, default=500-D       --duration=TIME   specify a length for the test run.                           Append 'm', 'h', or 'd' to specify minutes, hours or days.         --latency=PM_QOS  write PM_QOS to /dev/cpu_dma_latency-E       --event           event tracing (used with -b)-f       --ftrace          function trace (when -b is active)-F       --fifo=<path>     create a named pipe at path and write stats to it-h       --histogram=US    dump a latency histogram to stdout after the run                           US is the max latency time to be be tracked in microseconds                           This option runs all threads at the same priority.-H       --histofall=US    same as -h except with an additional summary column         --histfile=<path> dump the latency histogram to <path> instead of stdout-i INTV  --interval=INTV   base interval of thread in us default=1000-I       --irqsoff         Irqsoff tracing (used with -b)-l LOOPS --loops=LOOPS     number of loops: default=0(endless)         --laptop          Save battery when running cyclictest                           This will give you poorer realtime results                           but will not drain your battery so quickly-m       --mlockall        lock current and future memory allocations-M       --refresh_on_max  delay updating the screen until a new max                           latency is hit. Userful for low bandwidth.-n       --nanosleep       use clock_nanosleep         --notrace         suppress tracing-N       --nsecs           print results in ns instead of us (default us)-o RED   --oscope=RED      oscilloscope mode, reduce verbose output by RED-O TOPT  --traceopt=TOPT   trace option-p PRIO  --priority=PRIO   priority of highest prio thread-P       --preemptoff      Preempt off tracing (used with -b)         --policy=NAME     policy of measurement thread, where NAME may be one                           of: other, normal, batch, idle, fifo or rr.         --priospread      spread priority levels starting at specified value-q       --quiet           print a summary only on exit-r       --relative        use relative timer instead of absolute-R       --resolution      check clock resolution, calling clock_gettime() many                           times.  List of clock_gettime() values will be                           reported with -X         --secaligned [USEC] align thread wakeups to the next full second                           and apply the optional offset-s       --system          use sys_nanosleep and sys_setitimer-S       --smp             Standard SMP testing: options -a -t -n and                           same priority of all threads        --spike=<trigger>  record all spikes > trigger        --spike-nodes=[num of nodes]                           These are the maximum number of spikes we can record.                           The default is 1024 if not specified         --smi             Enable SMI counting-t       --threads         one thread per available processor-t [NUM] --threads=NUM     number of threads:                           without NUM, threads = max_cpus                           without -t default = 1         --tracemark       write a trace mark when -b latency is exceeded-T TRACE --tracer=TRACER   set tracing function    configured tracers: none-u       --unbuffered      force unbuffered output for live processing-U       --numa            Standard NUMA testing (similar to SMP option)                           thread data structures allocated from local node-v       --verbose         output values on stdout for statistics                           format: n:c:v n=tasknum c=count v=value in us-w       --wakeup          task wakeup tracing (used with -b)-W       --wakeuprt        rt task wakeup tracing (used with -b)         --dbg_cyclictest  print info useful for debugging cyclictest

简单介绍下一些参数：

• -m 锁定进程内存，防止页交换影响实时性，高精度测试时避免内存抖动。
• -n 使用 clock_nanosleep 替代 nanosleep，提高时间精度。
• -p 设置线程优先级（需 root 权限）。（Linux 中 SCHED_FIFO 优先级范围通常为 1-99）
• d0 CPU上有多个实时线程时，每个线程唤醒时间的间隔增量。当设置为0时，意味着所有线程将在同一时间被唤醒。
• -a 绑定线程到指定 CPU 核心，例如1-17 绑定到 CPU 1 到 17。
• -t 指定测试线程数量。

总结

以上为个人经验，希望能给大家一个参考，也希望大家多多支持本站。

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