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stats: fix calculation for the CPU time

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Closes: https://github.com/containers/libpod/issues/4409

Signed-off-by: Giuseppe Scrivano <giuseppe@scrivano.org>
This commit is contained in:
Giuseppe Scrivano
2019-11-01 20:52:08 +01:00
committed by Giuseppe Scrivano
parent 2c9e907912
commit a84ab35dc8
1 changed files with 11 additions and 13 deletions
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24
libpod/stats.go
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@ -3,7 +3,6 @@
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
}