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 +340,17 @@ 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).
+* **`execCPUAffinity`** (object, OPTIONAL) specifies CPU affinity used to execute the process.
+    This setting is not applicable to the container's init process.
+    The following properties are available:
+    * **`initial`** (string, OPTIONAL) is a list of CPUs a runtime parent
+      process to be run on initially, before the transition to container's
+      cgroup. This is a a comma-separated list, with dashes to represent
+      ranges. For example, `0-3,7` represents CPUs 0,1,2,3, and 7.
+    * **`final`** (string, OPTIONAL) is a list of CPUs the process will be run
+      on after the transition to container's cgroup. The format is the same as
+      for `initial`. If omitted or empty, the container's default CPU affinity,
+      as defined by [cpu.cpus property](./config.md#configLinuxCPUs)), is used.
 
 ### <a name="configUser" />User
 
@@ -416,7 +427,11 @@ _Note: symbolic name for uid and gid, such as uname and gname respectively, are
             "hard": 1024,
             "soft": 1024
         }
-    ]
+    ],
+    "execCPUAffinity": {
+        "initial": "7",
+        "final": "0-3,7"
+    }
 }
 ```
 ### Example (Solaris)

schema/config-schema.json

@@ -220,7 +220,20 @@
                             }
                         }
                     }
-                }
+                },
+                "execCPUAffinity": {
+                    "type": "object",
+                    "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"`
+	// ExecCPUAffinity specifies CPU affinity for exec processes.
+	ExecCPUAffinity *CPUAffinity `json:"execCPUAffinity,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,omitempty"`
+	Final   string `json:"final,omitempty"`
+}
+
 // 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.