如何测量golang中函数的执行时间，不包括等待时间

Question

I have a demand to measure execute time(cpu cost) of plugins in go, we can treat plugins as functions, there may be many goroutine running in the same time. More precisely, the execute time should exclude idle time(goroutine waiting time), only cpu acquire time(of current goroutine). it's like:

go func(){
    // this func is a plugin
    ** start to record cpu acquire time of current func/plugin/goroutine **
    ** run code **
    ** stop to record cpu acquire time of current func/plugin/goroutine **
    log.Debugf("This function is buzy for %d millisecs.", cpuAcquireTime)
    ** report cpuAcquirTime to monitor **
}()

In my circunstance, it's hard to make unit test to measure function, the code is hard to decouple.

I search google and stackoverflow and find no clue, is there any solution to satisfy my demand, and does it take too much resource?

Answer 1

There is no built-in way in Go to measure CPU time, but you can do it in a platform-specific way.

For example, on POSIX systems (e.g. Linux) use clock_gettime with CLOCK_THREAD_CPUTIME_ID as the parameter.

Similarly you can use CLOCK_PROCESS_CPUTIME_ID to measure process CPU time and CLOCK_MONOTONIC for elapsed time.

Example:

package main

/*
#include <pthread.h>
#include <time.h>
#include <stdio.h>

static long long getThreadCpuTimeNs() {
    struct timespec t;
    if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &t)) {
        perror("clock_gettime");
        return 0;
    }
    return t.tv_sec * 1000000000LL + t.tv_nsec;
}
*/
import "C"
import "fmt"
import "time"

func main() {
    cputime1 := C.getThreadCpuTimeNs()
    doWork()
    cputime2 := C.getThreadCpuTimeNs()
    fmt.Printf("CPU time = %d ns
", (cputime2 - cputime1))
}

func doWork() {
    x := 1
    for i := 0; i < 100000000; i++ {
        x *= 11111
    }
    time.Sleep(time.Second)
}

Output:

CPU time = 31250000 ns

Note the output is in nanoseconds. So here CPU time is 0.03 sec.