stats: fix calculation for the CPU time
Closes:
package libpod
import (
- "runtime"
"strings"
"syscall"
"time"
@@ -56,8 +55,8 @@ func (c *Container) GetContainerStats(previousStats *ContainerStats) (*Container
}
previousCPU := previousStats.CPUNano
- previousSystem := previousStats.SystemNano
- stats.CPU = calculateCPUPercent(cgroupStats, previousCPU, previousSystem)
+ now := uint64(time.Now().UnixNano())
+ stats.CPU = calculateCPUPercent(cgroupStats, previousCPU, now, previousStats.SystemNano)
stats.MemUsage = cgroupStats.Memory.Usage.Usage
stats.MemLimit = getMemLimit(cgroupStats.Memory.Usage.Limit)
stats.MemPerc = (float64(stats.MemUsage) / float64(stats.MemLimit)) * 100
@@ -67,7 +66,7 @@ func (c *Container) GetContainerStats(previousStats *ContainerStats) (*Container
}
stats.BlockInput, stats.BlockOutput = calculateBlockIO(cgroupStats)
stats.CPUNano = cgroupStats.CPU.Usage.Total
- stats.SystemNano = cgroupStats.CPU.Usage.Kernel
+ stats.SystemNano = now
// Handle case where the container is not in a network namespace
if netStats != nil {
stats.NetInput = netStats.TxBytes
@@ -98,20 +97,19 @@ func getMemLimit(cgroupLimit uint64) uint64 {
return cgroupLimit
}
-func calculateCPUPercent(stats *cgroups.Metrics, previousCPU, previousSystem uint64) float64 {
+// calculateCPUPercent calculates the cpu usage using the latest measurement in stats.
+// previousCPU is the last value of stats.CPU.Usage.Total measured at the time previousSystem.
+// (now - previousSystem) is the time delta in nanoseconds, between the measurement in previousCPU
+// and the updated value in stats.
+func calculateCPUPercent(stats *cgroups.Metrics, previousCPU, now, previousSystem uint64) float64 {
var (
cpuPercent = 0.0
cpuDelta = float64(stats.CPU.Usage.Total - previousCPU)
- systemDelta = float64(uint64(time.Now().UnixNano()) - previousSystem)
+ systemDelta = float64(now - previousSystem)
)
if systemDelta > 0.0 && cpuDelta > 0.0 {
- // gets a ratio of container cpu usage total, multiplies it by the number of cores (4 cores running
- // at 100% utilization should be 400% utilization), and multiplies that by 100 to get a percentage
- nCPUS := len(stats.CPU.Usage.PerCPU)
- if nCPUS == 0 {
- nCPUS = runtime.NumCPU()
- }
- cpuPercent = (cpuDelta / systemDelta) * float64(nCPUS) * 100
+ // gets a ratio of container cpu usage total, and multiplies that by 100 to get a percentage
+ cpuPercent = (cpuDelta / systemDelta) * 100
}
return cpuPercent
}
