Centralize cores and period/quota conversion code

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

2 files changed, 43 insertions, 0 deletions

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)
+}