Add CPU affinity to executed processes

This allows to set initial and final CPU affinity for a process being
run in a container, which is needed to solve the issue described in [1].

[1] opencontainers/runc#3922

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

config.md

@@ -340,6 +340,10 @@ For Linux-based systems, the `process` object supports the following process-spe
 
     * **`class`** (string, REQUIRED) specifies the I/O scheduling class. Possible values are `IOPRIO_CLASS_RT`, `IOPRIO_CLASS_BE`, and `IOPRIO_CLASS_IDLE`.
     * **`priority`** (int, REQUIRED) specifies the priority level within the class. The value should be an integer ranging from 0 (highest) to 7 (lowest).
+* **`cpuAffinity`** (object, OPTIONAL) specifies CPU affinity used to execute the process.
+    The following properties are available:
+    * **`initial`** (string, REQUIRED) is a list of CPUs the process will be run on initially, before the transition to container's cgroup.
+    * **`final`** (string, OPTIONAL) is a list of CPUs the process will be run on after the transition to container's cgroup. Empty string means to keep the initial setting. A special value `cgroup` means container's CPU affinity (as defined by [cpu.cpus property](./config.md#configLinuxCPUs)).
 
 ### <a name="configUser" />User
 

schema/config-schema.json

@@ -220,7 +220,23 @@
                             }
                         }
                     }
-                }
+                },
+                "cpuAffinity": {
+                    "type": "object",
+                    "required": [
+                        "initial"
+                    ],
+                    "properties": {
+                        "initial": {
+                            "type": "string",
+			    "pattern": "^[0-9, -]*$"
+                        },
+                        "final": {
+                            "type": "string",
+			    "pattern": "^[0-9, -]*$"
+                        }
+                    }
+		}
             }
         },
         "linux": {

specs-go/config.go

@@ -94,6 +94,8 @@ type Process struct {
 	SelinuxLabel string `json:"selinuxLabel,omitempty" platform:"linux"`
 	// IOPriority contains the I/O priority settings for the cgroup.
 	IOPriority *LinuxIOPriority `json:"ioPriority,omitempty" platform:"linux"`
+	// CPUAffinity specifies CPU affinity for the process.
+	CPUAffinity *CPUAffinity `json:"cpuAffinity,omitempty" platform:"linux"`
 }
 
 // LinuxCapabilities specifies the list of allowed capabilities that are kept for a process.
@@ -127,6 +129,12 @@ const (
 	IOPRIO_CLASS_IDLE IOPriorityClass = "IOPRIO_CLASS_IDLE"
 )
 
+// CPUAffinity specifies process' CPU affinity.
+type CPUAffinity struct {
+	Initial string `json:"initial"`
+	Final   string `json:"final"`
+}
+
 // Box specifies dimensions of a rectangle. Used for specifying the size of a console.
 type Box struct {
 	// Height is the vertical dimension of a box.