Merge pull request #13597 from Luap99/stats

podman stats: calc CPU percentage correctly

1 files changed, 13 insertions, 9 deletions

diff --git a/libpod/stats.go b/libpod/stats.go
index b5d39240d..25baa378d 100644
--- a/libpod/stats.go
+++ b/libpod/stats.go
@@ -14,7 +14,9 @@ import (
 	"github.com/pkg/errors"
 )
 
-// GetContainerStats gets the running stats for a given container
+// GetContainerStats gets the running stats for a given container.
+// The previousStats is used to correctly calculate cpu percentages. You
+// should pass nil if there is no previous stat for this container.
 func (c *Container) GetContainerStats(previousStats *define.ContainerStats) (*define.ContainerStats, error) {
 	stats := new(define.ContainerStats)
 	stats.ContainerID = c.ID()
@@ -36,6 +38,14 @@ func (c *Container) GetContainerStats(previousStats *define.ContainerStats) (*de
 		return stats, define.ErrCtrStateInvalid
 	}
 
+	if previousStats == nil {
+		previousStats = &define.ContainerStats{
+			// if we have no prev stats use the container start time as prev time
+			// otherwise we cannot correctly calculate the CPU percentage
+			SystemNano: uint64(c.state.StartedTime.UnixNano()),
+		}
+	}
+
 	cgroupPath, err := c.cGroupPath()
 	if err != nil {
 		return nil, err
@@ -67,8 +77,8 @@ func (c *Container) GetContainerStats(previousStats *define.ContainerStats) (*de
 	stats.Duration = cgroupStats.CPU.Usage.Total
 	stats.UpTime = time.Duration(stats.Duration)
 	stats.CPU = calculateCPUPercent(cgroupStats, previousCPU, now, previousStats.SystemNano)
-	stats.AvgCPU = calculateAvgCPU(stats.CPU, previousStats.AvgCPU, previousStats.DataPoints)
-	stats.DataPoints = previousStats.DataPoints + 1
+	// calc the average cpu usage for the time the container is running
+	stats.AvgCPU = calculateCPUPercent(cgroupStats, 0, now, uint64(c.state.StartedTime.UnixNano()))
 	stats.MemUsage = cgroupStats.Memory.Usage.Usage
 	stats.MemLimit = c.getMemLimit()
 	stats.MemPerc = (float64(stats.MemUsage) / float64(stats.MemLimit)) * 100
@@ -146,9 +156,3 @@ func calculateBlockIO(stats *cgroups.Metrics) (read uint64, write uint64) {
 	}
 	return
 }
-
-// calculateAvgCPU calculates the avg CPU percentage given the previous average and the number of data points.
-func calculateAvgCPU(statsCPU float64, prevAvg float64, prevData int64) float64 {
-	avgPer := ((prevAvg * float64(prevData)) + statsCPU) / (float64(prevData) + 1)
-	return avgPer
-}