Linux 实时性能测试工具—Cyclictest 的使用与分析【转】
转自：https://blog.51cto.com/qiangsh/2088862
关于Cyclictest工具，在Wiki上有说明：https://wiki.linuxfoundation.org/realtime/documentation/howto/tools/cyclictest
Cyclictest is a high resolution test program, written by User:Tglx, maintained by Clark Williams and John Kacur
Documentation Installation
Get the latest sources from the git repository, do a git clone git://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git or fetch a released tarball from the archive, untar into a directory of your choice and run make in the source directory. If you want to cross compile, just run make CROSS_COMPILE= (for example make CROSS_COMPILE=arm-v4t-linux-gnueabi-).
You can run the resulting binary from there or install it.
#需要安装libnuma-devel包后make编译
yum install numactl-devel
git clone git://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git
cd rt-tests
git checkout stable/v1.0
make all
make install
make cyclictest Run it
Make sure to be root or use sudo to run cyclictest.
Without parameters cyclictest creates one thread with a 1ms interval timer.
cyclictest -h provides help text for the various options
[root@localhost rt-tests]# ./cyclictest --help
cyclictest V 1.00
Usage:
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 当延时大于USEC指定的值时，发送停止跟踪。USEC,单位为谬秒（us）。
-B --preemptirqs both preempt and irqsoff tracing (used with -b)
-c CLOCK --clock=CLOCK 选择时钟 cyclictest -c 1
0 = CLOCK_MONOTONIC (默认)
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 指定要测试多长时间。默认单位是秒，但是也可以指定m(分),h(小时),d(天)
--latency=PM_QOS write PM_QOS to /dev/cpu_dma_latency
-E --event event tracing (used with -b)
-f --ftrace ftrace函数跟踪（通常与-b 配套使用，其实通常使用 -b 即可，不使用 -f ）
-F --fifo=<path> create a named pipe at path and write stats to it
-h --histogram=US 在执行完后在标准输出设备上画出延迟的直方图（很多线程有相同的权限）US为最大的跟踪时间限制，这个在下面介绍实例时可以用到，结合gnuplot 可以画出我们测试的结果图。
-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 基本线程间隔，默认为1000（单位为us）
-I --irqsoff Irqsoff tracing (used with -b)
-l LOOPS --loops=LOOPS 循环的个数，默认为0（无穷个），与 -i 间隔数结合可大致算出整个测试的时间，比如 -i 1000 -l 1000000 ,总的循环时间为1000*1000000=1000000000 us =1000s ，所以大致为16分钟多。
--laptop Save battery when running cyclictest
This will give you poorer realtime results
but will not drain your battery so quickly
-m --mlockall 锁定当前和将来的内存分配
-M --refresh_on_max delay updating the screen until a new max latency is hit.//延迟更新屏幕直到新的延时周期的到来 Userful for low bandwidth.
-n --nanosleep 使用 clock_nanosleep
--notrace suppress tracing
-N --nsecs print results in ns instead of us (default us) //每ns打印一次结果，而不是us(默认是us)
-o RED --oscope=RED oscilloscope mode, reduce verbose output by RED //示波器模式，减少冗长的输出通过RED
-O TOPT --traceopt=TOPT trace option //跟踪选项
-p PRIO --priority=PRIO 最高优先级线程的优先级 使用方法： -p 90 / --prio=90
-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 使用-q 参数运行时不打印信息，只在退出时打印概要内容，结合-h HISTNUM参数会在退出时打印HISTNUM 行统计信息以及一个总的概要信息。
-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 //标准 SMP 测试：选项 -a -t -n ,并且所有的线程要优先级相同
--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//每个可用的处理器一个线程
-t [NUM] --threads=NUM number of threads://线程的个数
without NUM, threads = max_cpus //不指定 NUM 时,线程个数为max_cups
without -t default = 1 //没有 -t 选项时，线程个数为1
--tracemark write a trace mark when -b latency is exceeded
-T TRACE --tracer=TRACER set tracing function
configured tracers: unavailable (debugfs not mounted)
-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 //把统计数据输出到标准输出
format: n:c:v n=tasknum c=count v=value in us //n=任务个数 c=计数 v=数值(单位:us)
-w --wakeup task wakeup tracing (used with -b) //任务唤醒跟踪(和 -b 一起使用)
-W --wakeuprt rt task wakeup tracing (used with -b) //实时任务唤醒跟踪
--dbg_cyclictest print info useful for debugging cyclictest推荐参数以及结果实例
[root@localhost rt-tests]# sudo ./cyclictest -p 90 - m -c 0 -i 200 -n -h 100 -q -l 1000000
我们使用 -p 90给cyclictest 赋优先级90，使用-m参数锁定内存分配，使用 -c 0指定使用默认的MONOTONIC 时钟，
-i 200 指定一个循环为200us，结合 -l 1000000为总共1000000个循环，-n 为使用nanosleep 而不是简单的sleep，
-q为在运行时不打印即时信息，-h 100 为总共统计100个信息在最后的结果中。
-----
#/dev/cpu_dma_latency set to 0us
-------------（下面都是结束测试/终端测试后打印的信息，这就是 -q 的功效！）
#Histogram
000000 000000
000001 000000
000002 000000
000003 000000
000004 000000
000005 000002 -- 延时为5us的在1000000次循环中占2次（下面每行都是这个意思）
000006 000009
..........此处省略
000099 000005 -- 我们使用 -h 100 ，所以在结果中记录了延时为 0us ～ 99us 的次数
#Total: 000999914
#Min Latencies: 00005 -- 最小延时 5 us
#Avg Latencies: 00012 -- 平均延时 12us
#Max Latencies: 19920 -- 最大延时19920 us，那么我们指定histogram = 100也就是只记录了0us～99us的值而最大延时为19920 也就是说肯定有很多此延时超过99 us，那么记录到哪了？答案是，没有记录具体的超过99us的延时值，只在下面记录了超过99us 的延时次数（记录在Overflows），以及第几次超过了（记录在Thread 0）。
#Histogram Overflows: 00086 -- 超过99 us的次数
#Histogram Overflow at cycle number:
#Thread 0: 65668 162024 164458 166533 171828 174546 179471 182538 188257 198415 202689 209055
211934 224529 227292 239809 267144 311992 312072 335066 341986 353395 355217 355295 355297 385017
411492 417012 443642 453450 453463 453478 453492 453504 453505 453522 453540 482063 482116 482797
483077 486153 515557 517062 517066 522812 538214 560636 574301 574500 598338 602175 610697 620924
678231 692237 692242 692247 713557 779826 797948 851442 860635 860642 860654 860661 861147 875755
880618 883622 884128 884238 885915 887215 887457 896442 925069 928998 942590 947161 947871 955507
955508 982245 982250 992192 //这里记录的是第几次循环的延时超过了99us。$ sudo cyclictest -t 2 // 使用两个测试线程
policy: other/other: loadavg: 0.00 0.01 0.05 1/346 2595
T: 0 ( 2594) P: 0 I:1000 C: 14090 Min: 32 Act: 200 Avg: 177 Max: 2855
T: 1 ( 2595) P: 0 I:1500 C: 9397 Min: 23 Act: 202 Avg: 170 Max: 2863输出结果含义:
T: 0 序号为0的线程
P: 0 线程优先级为0
C: 9397 计数器。线程的时间间隔每达到一次，计数器加1
I: 1000 时间间隔为1000微秒(us)
Min: 最小时延(us)
Act: 最近一次的时延(us)
Avg：平均时延(us)
Max： 最大时延(us)
Expected Results
tglx’s reference machine
All tests have been run on a Pentium III 400MHz based PC.
The tables show comparisons of vanilla Linux 2.6.16, Linux-2.6.16-hrt5 and Linux-2.6.16-rt12. The tests for intervals less than the jiffy resolution have not been run on vanilla Linux 2.6.16. The test thread runs in all cases with SCHED_FIFO and priority 80. All numbers are in microseconds.
案例: clock_nanosleep(TIME_ABSTIME), Interval 10000
microseconds,. 10000 loops, no load.
Commandline: cyclictest -t1 -p 80 -n -i 10000 -l 10000
Kernel min max avg
2.6.16 24 4043 1989
2.6.16-hrt5 12 94 20
2.6.16-rt12 6 40 10案例: clock_nanosleep(TIME_ABSTIME), Interval 10000 micro
seconds,. 10000 loops, 100% load.
Commandline: cyclictest -t1 -p 80 -n -i 10000 -l 10000
Kernel min max avg
2.6.16 55 4280 2198
2.6.16-hrt5 11 458 55
2.6.16-rt12 6 67 29案例: POSIX interval timer, Interval 10000 micro seconds,. 10000
loops, no load.
Commandline: cyclictest -t1 -p 80 -i 10000 -l 10000
Kernel min max avg
2.6.16 21 4073 2098
2.6.16-hrt5 22 120 35
2.6.16-rt12 20 60 31Test case: POSIX interval timer, Interval 10000 micro seconds,. 10000
loops, 100% load.
Commandline: cyclictest -t1 -p 80 -i 10000 -l 10000
Kernel min max avg
2.6.16 82 4271 2089
2.6.16-hrt5 31 458 53
2.6.16-rt12 21 70 35案例: clock_nanosleep(TIME_ABSTIME), Interval 500 micro
seconds,. 100000 loops, no load.
Commandline: cyclictest -t1 -p 80 -i 500 -n -l 100000
Kernel min max avg
2.6.16-hrt5 5 108 24
2.6.16-rt12 5 48 7Test case: clock_nanosleep(TIME_ABSTIME), Interval 500 micro
seconds,. 100000 loops, 100% load.
Commandline: cyclictest -t1 -p 80 -i 500 -n -l 100000
Kernel min max avg
2.6.16-hrt5 9 684 56
2.6.16-rt12 10 60 22案例: POSIX interval timer, Interval 500 micro seconds,. 100000
loops, no load.
Commandline: cyclictest -t1 -p 80 -i 500 -l 100000
Kernel min max avg
2.6.16-hrt5 8 119 22
2.6.16-rt12 12 78 16案例: POSIX interval timer, Interval 500 micro seconds,. 100000
loops, 100% load.
Commandline: cyclictest -t1 -p 80 -i 500 -l 100000
Kernel min max avg
2.6.16-hrt5 16 489 58
2.6.16-rt12 12 95 29FAQ
ps shows the wrong scheduling class SCHED_OTHER
Each cyclictest-task consist of one or more threads. ps -ce shows only the main-process not the threads of the main-process. ps -eLc | grep cyclic shows the main-process an the containing threads with the correct scheduler class SCHED_FIFO.
#>./cyclictest -t5 -p 80 -n -i 10000
#> ps -cLe | grep cyclic
4764 4764 TS 19 pts/1 00:00:01 cyclictest
4764 4765 FF 120 pts/1 00:00:00 cyclictest
4764 4766 FF 119 pts/1 00:00:00 cyclictest
4764 4767 FF 118 pts/1 00:00:00 cyclictest
4764 4768 FF 117 pts/1 00:00:00 cyclictest
4764 4769 FF 116 pts/1 00:00:00 cyclictestchrt shows the wrong scheduling class SCHED_OTHER
Don’t use the PID of the main-process, but the pid of one of the threads from the main-process. The threads are shown with ps -cLe | grep cyclic.
#> chrt -p 4766
pid 4766's current scheduling policy: SCHED_FIFO
pid 4766's current scheduling priority: 79
