Re: [PATCH] ipv4: Avoid overhead when no custom FIB rules are installed.

On Thu, 2012-07-05 at 22:31 -0700, David Miller wrote:

If the user hasn't actually installed any custom rules, or fiddled
with the default ones, don't go through the whole FIB rules layer.

It's just pure overhead.

Instead do what we do with CONFIG_IP_MULTIPLE_TABLES disabled, check
the individual tables by hand, one by one.

Also, move fib_num_tclassid_users into the ipv4 network namespace.

Signed-off-by: David S. Miller <davem@davemloft.net>

+static inline int fib_lookup(struct net *net, struct flowi4 *flp,
+			     struct fib_result *res)
+{
+	if (!net->ipv4.fib_has_custom_rules) {
+		if (net->ipv4.fib_local &&
+		    !fib_table_lookup(net->ipv4.fib_local, flp, res,
+				      FIB_LOOKUP_NOREF))
+			return 0;
+		if (net->ipv4.fib_main &&
+		    !fib_table_lookup(net->ipv4.fib_main, flp, res,
+				      FIB_LOOKUP_NOREF))
+			return 0;
+		if (net->ipv4.fib_default &&
+		    !fib_table_lookup(net->ipv4.fib_default, flp, res,
+				      FIB_LOOKUP_NOREF))
+			return 0;
+		return -ENETUNREACH;
+	}
+	return __fib_lookup(net, flp, res);
+}
+

Hmm, this seems quite big to be inlined ?