Fix the CPU burn instability.

Signed-off-by: Super-long <[email protected]>

exec/cpu/cpu.go

@@ -364,20 +364,19 @@ func burn(ctx context.Context, quota <-chan int64, slopePercent float64, precpu
 			// higher CPU load than expectedPercent.
 			// cpuPercent cannot be less than zero.
 			fmt.Println("+++++++++++", cpuPercent)
-			if cpuPercent == 0 || cpuPercent > slopePercent {
+			if cpuPercent > slopePercent {
 				totalCpuPercent, err := cpu.Percent(0, true)
 				if err != nil {
 					log.Fatalf(ctx, "get cpu usage fail, %s", err.Error())
 					continue
 				}
 				if totalCpuPercent[cpuIndex] >= slopePercent {
-					fmt.Println("current CPU load is higher than slopePercent.")
+					// 正常情况也可能跑到这里导致CPU频率下降
+					fmt.Println("current CPU load is higher than slopePercent.", q, ds, cpuPercent)
 					log.Debugf(ctx, "current CPU load is higher than slopePercent.")
 					// When the specified CPU frequency is greater than the expected CPU 
 					// frequency of chaos_os, we expect the behavior to be that chaos_os 
 					// does not occupy the CPU.
-					time.Sleep(time.Second)
-					cpu.Percent(time.Second, true)
 					continue
 				}
 				other := totalCpuPercent[cpuIndex] - beforeCpuPercent
@@ -394,6 +393,7 @@ func burn(ctx context.Context, quota <-chan int64, slopePercent float64, precpu
 				fmt.Println("xiufu: ", q, ds, cpuPercent, slopePercent, totalCpuPercent[cpuIndex])
 			}
 			fmt.Println("------------", q, ds, cpuPercent, float64(q)/float64(q+ds)*100)
+			// 当cpuPercent为零的时候stress_cpu会跑的很快
 			stress_cpu(time.Duration(q+ds), cpuPercent)
 			beforeCpuPercent = cpuPercent
 		}
@@ -579,6 +579,10 @@ func stress_cpu_factorial(name string) {
 // Make a single CPU load rate reach cpuPercent% within the time interval.
 // This function can also be used to implement something similar to stress-ng --cpu-load.
 func stress_cpu(interval time.Duration, cpuPercent float64) {
+	if cpuPercent == 0 {
+		time.Sleep(time.Duration(interval)*time.Nanosecond)
+		return
+	}
 	bias := 0.0
 	startTime := time.Now().UnixNano()
 	nanoInterval := int64(interval/time.Nanosecond)