tcp: shrink tcp6_timewait_sock by one cache line

While working on tcp listener refactoring, I found that it
would really make things easier if sock_common could include
the IPv6 addresses needed in the lookups, instead of doing
very complex games to get their values (depending on sock
being SYN_RECV, ESTABLISHED, TIME_WAIT)

For this to happen, I need to be sure that tcp6_timewait_sock
and tcp_timewait_sock consume same number of cache lines.

This is possible if we only use 32bits for tw_ttd, as we remove
one 32bit hole in inet_timewait_sock

inet_tw_time_stamp() is defined and used, even if its current
implementation looks like tcp_time_stamp : We might need finer
resolution for tcp_time_stamp in the future.

Before patch : sizeof(struct tcp6_timewait_sock) = 0xc8

After patch : sizeof(struct tcp6_timewait_sock) = 0xc0

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 1 deletions

diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index 48fd3561722..f528d1b0ac9 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -58,6 +58,11 @@ struct inet_hashinfo;
 # define INET_TWDR_RECYCLE_TICK (12 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
 #endif
 
+static inline u32 inet_tw_time_stamp(void)
+{
+	return jiffies;
+}
+
 /* TIME_WAIT reaping mechanism. */
 #define INET_TWDR_TWKILL_SLOTS	8 /* Please keep this a power of 2. */
 
@@ -130,7 +135,7 @@ struct inet_timewait_sock {
 				tw_tos		: 8,
 				tw_ipv6_offset  : 16;
 	kmemcheck_bitfield_end(flags);
-	unsigned long		tw_ttd;
+	u32			tw_ttd;
 	struct inet_bind_bucket	*tw_tb;
 	struct hlist_node	tw_death_node;
 };