Centralize cores and period/quota conversion code

Signed-off-by: Jordan Christiansen <xordspar0@gmail.com>

5 files changed, 48 insertions, 11 deletions

diff --git a/cmd/podman/common/specgen.go b/cmd/podman/common/specgen.go
index bd3e5fafd..ca1e25be1 100644
--- a/cmd/podman/common/specgen.go
+++ b/cmd/podman/common/specgen.go
@@ -25,11 +25,8 @@ func getCPULimits(c *ContainerCLIOpts) *specs.LinuxCPU {
 	cpu := &specs.LinuxCPU{}
 	hasLimits := false
 
-	const cpuPeriod = 100000
-
 	if c.CPUS > 0 {
-		quota := int64(c.CPUS * cpuPeriod)
-		period := uint64(cpuPeriod)
+		period, quota := util.CoresToPeriodAndQuota(c.CPUS)
 
 		cpu.Period = &period
 		cpu.Quota = &quota
diff --git a/libpod/kube.go b/libpod/kube.go
index cd5064c84..067e7827d 100644
--- a/libpod/kube.go
+++ b/libpod/kube.go
@@ -327,7 +327,7 @@ func containerToV1Container(c *Container) (v1.Container, []v1.Volume, error) {
 			period := *c.config.Spec.Linux.Resources.CPU.Period
 
 			if quota > 0 && period > 0 {
-				cpuLimitMilli := int64(1000 * float64(quota) / float64(period))
+				cpuLimitMilli := int64(1000 * util.PeriodAndQuotaToCores(period, quota))
 
 				// Kubernetes: precision finer than 1m is not allowed
 				if cpuLimitMilli >= 1 {
diff --git a/pkg/domain/infra/abi/play.go b/pkg/domain/infra/abi/play.go
index 57de0f3b1..fbba00984 100644
--- a/pkg/domain/infra/abi/play.go
+++ b/pkg/domain/infra/abi/play.go
@@ -36,8 +36,6 @@ const (
 	kubeDirectoryPermission = 0755
 	// https://kubernetes.io/docs/concepts/storage/volumes/#hostpath
 	kubeFilePermission = 0644
-	// Kubernetes sets CPUPeriod to 100000us (100ms): https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/
-	defaultCPUPeriod = 100000
 )
 
 func (ic *ContainerEngine) PlayKube(ctx context.Context, path string, options entities.PlayKubeOptions) (*entities.PlayKubeReport, error) {
@@ -515,10 +513,9 @@ func kubeContainerToCreateConfig(ctx context.Context, containerYAML v1.Container
 		return nil, errors.Wrap(err, "Failed to set CPU quota")
 	}
 	if milliCPU > 0 {
-		containerConfig.Resources.CPUPeriod = defaultCPUPeriod
-		// CPU quota is a fraction of the period: milliCPU / 1000.0 * period
-		// Or, without floating point math:
-		containerConfig.Resources.CPUQuota = milliCPU * defaultCPUPeriod / 1000
+		period, quota := util.CoresToPeriodAndQuota(float64(milliCPU) / 1000)
+		containerConfig.Resources.CPUPeriod = period
+		containerConfig.Resources.CPUQuota = quota
 	}
 
 	containerConfig.Resources.Memory, err = quantityToInt64(containerYAML.Resources.Limits.Memory())
diff --git a/pkg/util/utils.go b/pkg/util/utils.go
index a9aad657d..415fd169b 100644
--- a/pkg/util/utils.go
+++ b/pkg/util/utils.go
@@ -653,3 +653,26 @@ func CreateCidFile(cidfile string, id string) error {
 	cidFile.Close()
 	return nil
 }
+
+// DefaultCPUPeriod is the default CPU period is 100us, which is the same default
+// as Kubernetes.
+const DefaultCPUPeriod uint64 = 100000
+
+// CoresToPeriodAndQuota converts a fraction of cores to the equivalent
+// Completely Fair Scheduler (CFS) parameters period and quota.
+//
+// Cores is a fraction of the CFS period that a container may use. Period and
+// Quota are in microseconds.
+func CoresToPeriodAndQuota(cores float64) (uint64, int64) {
+	return DefaultCPUPeriod, int64(cores * float64(DefaultCPUPeriod))
+}
+
+// PeriodAndQuotaToCores takes the CFS parameters period and quota and returns
+// a fraction that represents the limit to the number of cores that can be
+// utilized over the scheduling period.
+//
+// Cores is a fraction of the CFS period that a container may use. Period and
+// Quota are in microseconds.
+func PeriodAndQuotaToCores(period uint64, quota int64) float64 {
+	return float64(quota) / float64(period)
+}
diff --git a/pkg/util/utils_test.go b/pkg/util/utils_test.go
index a9b37844e..cb737bd76 100644
--- a/pkg/util/utils_test.go
+++ b/pkg/util/utils_test.go
@@ -257,3 +257,23 @@ func TestValidateSysctlBadSysctl(t *testing.T) {
 	_, err := ValidateSysctls(strSlice)
 	assert.Error(t, err)
 }
+
+func TestCoresToPeriodAndQuota(t *testing.T) {
+	cores := 1.0
+	expectedPeriod := DefaultCPUPeriod
+	expectedQuota := int64(DefaultCPUPeriod)
+
+	actualPeriod, actualQuota := CoresToPeriodAndQuota(cores)
+	assert.Equal(t, actualPeriod, expectedPeriod, "Period does not match")
+	assert.Equal(t, actualQuota, expectedQuota, "Quota does not match")
+}
+
+func TestPeriodAndQuotaToCores(t *testing.T) {
+	var (
+		period        uint64 = 100000
+		quota         int64  = 50000
+		expectedCores        = 0.5
+	)
+
+	assert.Equal(t, PeriodAndQuotaToCores(period, quota), expectedCores)
+}