[lbry] runtime: Add --memprofile option

* Add --memprofile option. Add memprofile to sample config.
* Add --memprofile to doc.go.

config.go

@@ -117,6 +117,7 @@ type config struct {
 	ConfigFile           string        `short:"C" long:"configfile" description:"Path to configuration file"`
 	ConnectPeers         []string      `long:"connect" description:"Connect only to the specified peers at startup"`
 	CPUProfile           string        `long:"cpuprofile" description:"Write CPU profile to the specified file"`
+	MemProfile           string        `long:"memprofile" description:"Write memory profile to the specified file"`
 	DataDir              string        `short:"b" long:"datadir" description:"Directory to store data"`
 	DbType               string        `long:"dbtype" description:"Database backend to use for the Block Chain"`
 	DebugLevel           string        `short:"d" long:"debuglevel" description:"Logging level for all subsystems {trace, debug, info, warn, error, critical} -- You may also specify <subsystem>=<level>,<subsystem2>=<level>,... to set the log level for individual subsystems -- Use show to list available subsystems"`

doc.go

@@ -78,6 +78,7 @@ Application Options:
                               memory (default: 100)
       --maxpeers=             Max number of inbound and outbound peers
                               (default: 125)
+      --memprofile=           Write memory profile to the specified file
       --miningaddr=           Add the specified payment address to the list of
                               addresses to use for generated blocks -- At least
                               one address is required if the generate option is

lbcd.go

@@ -92,6 +92,25 @@ func btcdMain(serverChan chan<- *server) error {
 		defer pprof.StopCPUProfile()
 	}
 
+	// Write memory profile if requested.
+	if cfg.MemProfile != "" {
+		f, err := os.Create(cfg.MemProfile + ".heap")
+		if err != nil {
+			btcdLog.Errorf("Unable to create mem profile: %v", err)
+			return err
+		}
+		defer f.Close()
+		defer pprof.Lookup("heap").WriteTo(f, 0)
+
+		f, err = os.Create(cfg.MemProfile + ".allocs")
+		if err != nil {
+			btcdLog.Errorf("Unable to create mem profile: %v", err)
+			return err
+		}
+		defer f.Close()
+		defer pprof.Lookup("allocs").WriteTo(f, 0)
+	}
+
 	// Perform upgrades to btcd as new versions require it.
 	if err := doUpgrades(); err != nil {
 		btcdLog.Errorf("%v", err)

sample-lbcd.conf

@@ -376,6 +376,9 @@
 ; Write CPU profile to the specified file.
 ; cpuprofile=
 
+; Write memory profile to the specified file.
+; memprofile=
+
 ; The port used to listen for HTTP profile requests.  The profile server will
 ; be disabled if this option is not specified.  The profile information can be
 ; accessed at http://localhost:<profileport>/debug/pprof once running.