separate lock from common grid to avoid epoll contention (#20180)

epoll contention on TCP causes latency build-up when
we have high volume ingress. This PR is an attempt to
relieve this pressure.

upstream issue https://github.com/golang/go/issues/65064
It seems to be a deeper problem; haven't yet tried the fix
provide in this issue, but however this change without
changing the compiler helps. 

Of course, this is a workaround for now, hoping for a
more comprehensive fix from Go runtime.

cmd/grid.go

@@ -31,9 +31,15 @@ import (
 // globalGrid is the global grid manager.
 var globalGrid atomic.Pointer[grid.Manager]
 
+// globalLockGrid is the global lock grid manager.
+var globalLockGrid atomic.Pointer[grid.Manager]
+
 // globalGridStart is a channel that will block startup of grid connections until closed.
 var globalGridStart = make(chan struct{})
 
+// globalLockGridStart is a channel that will block startup of lock grid connections until closed.
+var globalLockGridStart = make(chan struct{})
+
 func initGlobalGrid(ctx context.Context, eps EndpointServerPools) error {
 	hosts, local := eps.GridHosts()
 	lookupHost := globalDNSCache.LookupHost
@@ -55,9 +61,10 @@ func initGlobalGrid(ctx context.Context, eps EndpointServerPools) error {
 		AuthFn:       newCachedAuthToken(),
 		BlockConnect: globalGridStart,
 		// Record incoming and outgoing bytes.
-		Incoming: globalConnStats.incInternodeInputBytes,
-		Outgoing: globalConnStats.incInternodeOutputBytes,
-		TraceTo:  globalTrace,
+		Incoming:  globalConnStats.incInternodeInputBytes,
+		Outgoing:  globalConnStats.incInternodeOutputBytes,
+		TraceTo:   globalTrace,
+		RoutePath: grid.RoutePath,
 	})
 	if err != nil {
 		return err
@@ -65,3 +72,36 @@ func initGlobalGrid(ctx context.Context, eps EndpointServerPools) error {
 	globalGrid.Store(g)
 	return nil
 }
+
+func initGlobalLockGrid(ctx context.Context, eps EndpointServerPools) error {
+	hosts, local := eps.GridHosts()
+	lookupHost := globalDNSCache.LookupHost
+	g, err := grid.NewManager(ctx, grid.ManagerOptions{
+		// Pass Dialer for websocket grid, make sure we do not
+		// provide any DriveOPTimeout() function, as that is not
+		// useful over persistent connections.
+		Dialer: grid.ConnectWSWithRoutePath(
+			grid.ContextDialer(xhttp.DialContextWithLookupHost(lookupHost, xhttp.NewInternodeDialContext(rest.DefaultTimeout, globalTCPOptions.ForWebsocket()))),
+			newCachedAuthToken(),
+			&tls.Config{
+				RootCAs:          globalRootCAs,
+				CipherSuites:     fips.TLSCiphers(),
+				CurvePreferences: fips.TLSCurveIDs(),
+			}, grid.RouteLockPath),
+		Local:        local,
+		Hosts:        hosts,
+		AuthToken:    validateStorageRequestToken,
+		AuthFn:       newCachedAuthToken(),
+		BlockConnect: globalGridStart,
+		// Record incoming and outgoing bytes.
+		Incoming:  globalConnStats.incInternodeInputBytes,
+		Outgoing:  globalConnStats.incInternodeOutputBytes,
+		TraceTo:   globalTrace,
+		RoutePath: grid.RouteLockPath,
+	})
+	if err != nil {
+		return err
+	}
+	globalLockGrid.Store(g)
+	return nil
+}