Merge pull request #403 from ascrutae/feature/debugging

fix issue that cpu metric data is incorrect

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/jvm/cpu/CPUMetricAccessor.java

@@ -27,6 +27,6 @@ public abstract class CPUMetricAccessor {
         long now = System.nanoTime();
 
         CPU.Builder cpuBuilder = CPU.newBuilder();
-        return cpuBuilder.setUsagePercent(cpuCost * 1.0d / (now - lastSampleTimeNs) * cpuCoreNum).build();
+        return cpuBuilder.setUsagePercent(cpuCost * 1.0d / ((now - lastSampleTimeNs) * cpuCoreNum)).build();
     }
 }