Subject: [PATCH 16/27] tcp: cache line align MAX_TCP_HEADER

From: Eric Dumazet <[email-masked]>
Date: Fri, 17 Apr 2020 07:10:23 -0700

[ Upstream commit 9bacd256f1354883d3c1402655153367982bba49 ]

TCP stack is dumb in how it cooks its output packets.

Depending on MAX_HEADER value, we might chose a bad ending point
for the headers.

If we align the end of TCP headers to cache line boundary, we
make sure to always use the smallest number of cache lines,
which always help.

Signed-off-by: Eric Dumazet <[email-masked]>
Cc: Soheil Hassas Yeganeh <[email-masked]>
Acked-by: Soheil Hassas Yeganeh <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 include/net/tcp.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 830c89db1245..cce285f70c8e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -50,7 +50,7 @@ extern struct inet_hashinfo tcp_hashinfo;
 extern struct percpu_counter tcp_orphan_count;
 void tcp_time_wait(struct sock *sk, int state, int timeo);
 
-#define MAX_TCP_HEADER	(128 + MAX_HEADER)
+#define MAX_TCP_HEADER	L1_CACHE_ALIGN(128 + MAX_HEADER)
 #define MAX_TCP_OPTION_SPACE 40
 #define TCP_MIN_SND_MSS		48
 #define TCP_MIN_GSO_SIZE	(TCP_MIN_SND_MSS - MAX_TCP_OPTION_SPACE)
-- 
2.20.1