Merge pull request #2 from sjenning/pick-1805-3.9

[3.9] UPSTREAM: 1805: fix systemd cpu quota for -1

Author: sjenning

libcontainer/cgroups/systemd/apply_systemd.go

@@ -5,6 +5,7 @@ package systemd
 import (
 	"errors"
 	"fmt"
+	"math"
 	"os"
 	"path/filepath"
 	"strings"
@@ -270,13 +271,19 @@ func (m *Manager) Apply(pid int) error {
 
 	// cpu.cfs_quota_us and cpu.cfs_period_us are controlled by systemd.
 	if c.Resources.CpuQuota != 0 && c.Resources.CpuPeriod != 0 {
-		cpuQuotaPerSecUSec := uint64(c.Resources.CpuQuota*1000000) / c.Resources.CpuPeriod
-		// systemd converts CPUQuotaPerSecUSec (microseconds per CPU second) to CPUQuota
-		// (integer percentage of CPU) internally.  This means that if a fractional percent of
-		// CPU is indicated by Resources.CpuQuota, we need to round up to the nearest
-		// 10ms (1% of a second) such that child cgroups can set the cpu.cfs_quota_us they expect.
-		if cpuQuotaPerSecUSec%10000 != 0 {
-			cpuQuotaPerSecUSec = ((cpuQuotaPerSecUSec / 10000) + 1) * 10000
+		// corresponds to USEC_INFINITY in systemd
+		// if USEC_INFINITY is provided, CPUQuota is left unbound by systemd
+		// always setting a property value ensures we can apply a quota and remove it later
+		cpuQuotaPerSecUSec := uint64(math.MaxUint64)
+		if c.Resources.CpuQuota > 0 {
+			// systemd converts CPUQuotaPerSecUSec (microseconds per CPU second) to CPUQuota
+			// (integer percentage of CPU) internally.  This means that if a fractional percent of
+			// CPU is indicated by Resources.CpuQuota, we need to round up to the nearest
+			// 10ms (1% of a second) such that child cgroups can set the cpu.cfs_quota_us they expect.
+			cpuQuotaPerSecUSec = uint64(c.Resources.CpuQuota*1000000) / c.Resources.CpuPeriod
+			if cpuQuotaPerSecUSec%10000 != 0 {
+				cpuQuotaPerSecUSec = ((cpuQuotaPerSecUSec / 10000) + 1) * 10000
+			}
 		}
 		properties = append(properties,
 			newProp("CPUQuotaPerSecUSec", cpuQuotaPerSecUSec))