Add a flag to enable live profiling.

The profile information can be seen with a browser on e.g.
http://localhost:6060/debug/pprof/
Alternatively, one can use the pprof tool as described at
http://golang.org/pkg/net/http/pprof/

ok davec

btcd.go

@@ -11,6 +11,8 @@ import (
 	"github.com/conformal/btcscript"
 	"github.com/conformal/seelog"
 	"net"
+	"net/http"
+	_ "net/http/pprof"
 	"os"
 	"runtime"
 )
@@ -108,6 +110,14 @@ func btcdMain() error {
 		loggers = setLogLevel(cfg.DebugLevel)
 	}
 
+	// See if we want to enable profiling
+	if cfg.Profile != "" {
+		go func() {
+			log.Errorf("%v", http.ListenAndServe(
+				net.JoinHostPort("", cfg.Profile), nil))
+		}()
+	}
+
 	// Perform upgrades to btcd as new versions require it.
 	err = doUpgrades()
 	if err != nil {

config.go

@@ -15,6 +15,7 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -62,6 +63,7 @@ type config struct {
 	TestNet3       bool          `long:"testnet" description:"Use the test network"`
 	RegressionTest bool          `long:"regtest" description:"Use the regression test network"`
 	DbType         string        `long:"dbtype" description:"Database backend to use for the Block Chain"`
+	Profile        string        `long:"profile" description:"Enable HTTP profiling on given port -- NOTE port must be between 1024 and 65536"`
 	DebugLevel     string        `short:"d" long:"debuglevel" description:"Logging level {trace, debug, info, warn, error, critical}"`
 }
 
@@ -282,6 +284,16 @@ func loadConfig() (*config, []string, error) {
 		return nil, nil, err
 	}
 
+	// Validate profile port number
+	profilePort, err := strconv.Atoi(cfg.Profile)
+	if err != nil || profilePort < 1024 || profilePort > 65535 {
+		str := "%s: The profile port must be between 1024 and 65535"
+		err := errors.New(fmt.Sprintf(str, "loadConfig"))
+		fmt.Fprintln(os.Stderr, err)
+		parser.WriteHelp(os.Stderr)
+		return nil, nil, err
+	}
+
 	// Append the network type to the data directory so it is "namespaced"
 	// per network.  In addition to the block database, there are other
 	// pieces of data that are saved to disk such as address manager state.