Implementing support for --cpu-rt-period and --cpu-rt-runtime so that

containers may specify these cgroup values at runtime. This will allow
processes to change their priority to real-time within the container
when CONFIG_RT_GROUP_SCHED is enabled in the kernel. See #22380.

Also added sanity checks for the new --cpu-rt-runtime and --cpu-rt-period
flags to ensure that that the kernel supports these features and that
runtime is not greater than period.

Daemon will support a --cpu-rt-runtime flag to initialize the parent
cgroup on startup, this prevents the administrator from alotting runtime
to docker after each restart.

There are additional checks that could be added but maybe too far? Check
parent cgroups to ensure values are <= parent, inspecting rtprio ulimit
and issuing a warning.

Signed-off-by: Erik St. Martin <alakriti@gmail.com>

command/container/update.go

@@ -15,17 +15,19 @@ import (
 )
 
 type updateOptions struct {
-	blkioWeight       uint16
-	cpuPeriod         int64
-	cpuQuota          int64
-	cpusetCpus        string
-	cpusetMems        string
-	cpuShares         int64
-	memoryString      string
-	memoryReservation string
-	memorySwap        string
-	kernelMemory      string
-	restartPolicy     string
+	blkioWeight        uint16
+	cpuPeriod          int64
+	cpuQuota           int64
+	cpuRealtimePeriod  int64
+	cpuRealtimeRuntime int64
+	cpusetCpus         string
+	cpusetMems         string
+	cpuShares          int64
+	memoryString       string
+	memoryReservation  string
+	memorySwap         string
+	kernelMemory       string
+	restartPolicy      string
 
 	nFlag int
 
@@ -51,6 +53,8 @@ func NewUpdateCommand(dockerCli *command.DockerCli) *cobra.Command {
 	flags.Uint16Var(&opts.blkioWeight, "blkio-weight", 0, "Block IO (relative weight), between 10 and 1000")
 	flags.Int64Var(&opts.cpuPeriod, "cpu-period", 0, "Limit CPU CFS (Completely Fair Scheduler) period")
 	flags.Int64Var(&opts.cpuQuota, "cpu-quota", 0, "Limit CPU CFS (Completely Fair Scheduler) quota")
+	flags.Int64Var(&opts.cpuRealtimePeriod, "cpu-rt-period", 0, "Limit the CPU real-time period in microseconds")
+	flags.Int64Var(&opts.cpuRealtimeRuntime, "cpu-rt-runtime", 0, "Limit the CPU real-time runtime in microseconds")
 	flags.StringVar(&opts.cpusetCpus, "cpuset-cpus", "", "CPUs in which to allow execution (0-3, 0,1)")
 	flags.StringVar(&opts.cpusetMems, "cpuset-mems", "", "MEMs in which to allow execution (0-3, 0,1)")
 	flags.Int64VarP(&opts.cpuShares, "cpu-shares", "c", 0, "CPU shares (relative weight)")
@@ -115,16 +119,18 @@ func runUpdate(dockerCli *command.DockerCli, opts *updateOptions) error {
 	}
 
 	resources := containertypes.Resources{
-		BlkioWeight:       opts.blkioWeight,
-		CpusetCpus:        opts.cpusetCpus,
-		CpusetMems:        opts.cpusetMems,
-		CPUShares:         opts.cpuShares,
-		Memory:            memory,
-		MemoryReservation: memoryReservation,
-		MemorySwap:        memorySwap,
-		KernelMemory:      kernelMemory,
-		CPUPeriod:         opts.cpuPeriod,
-		CPUQuota:          opts.cpuQuota,
+		BlkioWeight:        opts.blkioWeight,
+		CpusetCpus:         opts.cpusetCpus,
+		CpusetMems:         opts.cpusetMems,
+		CPUShares:          opts.cpuShares,
+		Memory:             memory,
+		MemoryReservation:  memoryReservation,
+		MemorySwap:         memorySwap,
+		KernelMemory:       kernelMemory,
+		CPUPeriod:          opts.cpuPeriod,
+		CPUQuota:           opts.cpuQuota,
+		CPURealtimePeriod:  opts.cpuRealtimePeriod,
+		CPURealtimeRuntime: opts.cpuRealtimeRuntime,
 	}
 
 	updateConfig := containertypes.UpdateConfig{