Set kernel.applicationCores to the number of processor on the host

The right number to use is the number of processors assigned to the cgroup. But until
we make the sandbox join the respective cgroup, just use the number of processors on
the host.

Closes #65, closes #66

PiperOrigin-RevId: 200725483
Change-Id: I34a566b1a872e26c66f56fa6e3100f42aaf802b1

runsc/boot/loader.go

@@ -18,6 +18,7 @@ package boot
 import (
 	"fmt"
 	"math/rand"
+	"runtime"
 	"sync/atomic"
 	"syscall"
 	gtime "time"
@@ -171,10 +172,11 @@ func New(spec *specs.Spec, conf *Config, controllerFD int, ioFDs []int, console
 		Timekeeper:        tk,
 		RootUserNamespace: creds.UserNamespace,
 		NetworkStack:      networkStack,
-		ApplicationCores:  8,
-		Vdso:              vdso,
-		RootUTSNamespace:  utsns,
-		RootIPCNamespace:  ipcns,
+		// TODO: use number of logical processors from cgroups.
+		ApplicationCores: uint(runtime.NumCPU()),
+		Vdso:             vdso,
+		RootUTSNamespace: utsns,
+		RootIPCNamespace: ipcns,
 	}); err != nil {
 		return nil, fmt.Errorf("error initializing kernel: %v", err)
 	}

runsc/boot/loader_test.go

@@ -15,7 +15,9 @@
 package boot
 
 import (
+	"fmt"
 	"io/ioutil"
+	"math/rand"
 	"os"
 	"sync"
 	"testing"
@@ -29,6 +31,7 @@ import (
 
 func init() {
 	log.SetLevel(log.Debug)
+	rand.Seed(time.Now().UnixNano())
 }
 
 // testSpec returns a simple spec that can be used in tests.
@@ -46,7 +49,7 @@ func testSpec() *specs.Spec {
 }
 
 func createLoader() (*Loader, error) {
-	fd, err := server.CreateSocket(ControlSocketAddr("123"))
+	fd, err := server.CreateSocket(ControlSocketAddr(fmt.Sprintf("%010d", rand.Int())[:10]))
 	if err != nil {
 		return nil, err
 	}