Eric Dumazet wrote:

Pavel Emelyanov a écrit :

quoted

After turning IP_XXX_STATS, TCP_XXX_STATS and NET_XXX_STATS from
macros into functions the net/ipv4/built-in.o shrank significantly:

add/remove: 14/0 grow/shrink: 0/67 up/down: 482/-2246 (-1764)

Turning the CONFIG_NET_NS option on makes this shrink even larger:

add/remove: 14/0 grow/shrink: 0/67 up/down: 478/-2646 (-2168)

So the question is - what was the reason to keep those as macros?
I thought about the possible performance questions, but netperf
didn't show any (I admit I just cannot cook it properly).

The sample patch is here, but it's not good (EXPORTs for ipv6
and a better place for functions rather than net/ipv4/af_inet.c
are required).

Signed-off-by: Pavel Emelyanov <redacted>

I dont know, but passing all those "struct net *net" to every 
network function in the kernel sounds overkill, especially for
!CONFIG_NET_NS users. This is pure bloat.

We could define two macros so that function prototypes dont include
useless pointers, especially on arches where only first and second
parameter is passed in eax and edx register ;)

#ifdef CONFIG_NET_NS
# define VNETPTR ,struct net *net
# define NETPTR  net
#else
# define VNETPTR
# defint NETPTR  &init_net
#endif

...
void TCP_DEC_STATS(int field VNETPTR);
...
void TCP_DEC_STATS(int field VNETPTR)
{
	SNMP_DEC_STATS((NETPTR)->mib.tcp_statistics, field);
}
...

I agree with this, but I've checked whether compiling out the first argument
of XXX_STATS would help and found out that there's almost no difference (-9
bytes) in the net/ipv4/built-in.o for NET_NS=n case. 

After turning the macros into functions, compiling the first argument out gives
us 500 more bytes out. Good catch, but I have a question - the way you proposed
to implement the function itself is rather nice, but how would you implement
the *call* to that function in order to make it variable-arguments depending on
the config option?

I see the similar way:

+#ifdef CONFIG_NET_NS
+#define NET_ARG(net) net,
+#else
+#define NET_ARG(net)
+#endif
...
-	TCP_INC_STATS(sock_net(sk), field);
+	TCP_INC_STATS(NET_ARG(sock_net(sk) field);

but do these 500 bytes compensate for this ugly style?