Allow cAdvisor to use as many cores as exist on the machine.

We scale with the number of containers (and cores on the machine) so we
should be able to use more than just one core (the default).

cadvisor.go

@@ -18,6 +18,7 @@ import (
 	"flag"
 	"fmt"
 	"net/http"
+	"runtime"
 
 	"github.com/golang/glog"
 	"github.com/google/cadvisor/api"
@@ -30,12 +31,15 @@ import (
 )
 
 var argPort = flag.Int("port", 8080, "port to listen")
+var maxProcs = flag.Int("max_procs", 0, "max number of CPUs that can be used simultaneously. Less than 1 for default (number of cores).")
 
 var argDbDriver = flag.String("storage_driver", "memory", "storage driver to use. Options are: memory (default) and influxdb")
 
 func main() {
 	flag.Parse()
 
+	setMaxProcs()
+
 	storageDriver, err := NewStorageDriver(*argDbDriver)
 	if err != nil {
 		glog.Fatalf("Failed to connect to database: %s", err)
@@ -93,3 +97,21 @@ func main() {
 
 	glog.Fatal(http.ListenAndServe(addr, nil))
 }
+
+func setMaxProcs() {
+	// TODO(vmarmol): Consider limiting if we have a CPU mask in effect.
+	// Allow as many threads as we have cores unless the user specified a value.
+	var numProcs int
+	if *maxProcs < 1 {
+		numProcs = runtime.NumCPU()
+	} else {
+		numProcs = *maxProcs
+	}
+	runtime.GOMAXPROCS(numProcs)
+
+	// Check if the setting was successful.
+	actualNumProcs := runtime.GOMAXPROCS(0)
+	if actualNumProcs != numProcs {
+		glog.Warningf("Specified max procs of %v but using %v", numProcs, actualNumProcs)
+	}
+}