Re: [PATCH net-next] sctp: Pack dst_cookie into 1st cacheline hole for 64bit host

As dst_cookie is used in fast path sctp_transport_dst_check.

Before:
struct sctp_transport {
	struct list_head           transports;           /*     0    16 */
	atomic_t                   refcnt;               /*    16     4 */
	__u32                      dead:1;               /*    20:31  4 */
	__u32                      rto_pending:1;        /*    20:30  4 */
	__u32                      hb_sent:1;            /*    20:29  4 */
	__u32                      pmtu_pending:1;       /*    20:28  4 */

	/* XXX 28 bits hole, try to pack */

	__u32                      sack_generation;      /*    24     4 */

	/* XXX 4 bytes hole, try to pack */

	struct flowi               fl;                   /*    32    64 */
	/* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */
	union sctp_addr            ipaddr;               /*    96    28 */

After:
struct sctp_transport {
	struct list_head           transports;           /*     0    16 */
	atomic_t                   refcnt;               /*    16     4 */
	__u32                      dead:1;               /*    20:31  4 */
	__u32                      rto_pending:1;        /*    20:30  4 */
	__u32                      hb_sent:1;            /*    20:29  4 */
	__u32                      pmtu_pending:1;       /*    20:28  4 */

	/* XXX 28 bits hole, try to pack */

	__u32                      sack_generation;      /*    24     4 */
	u32                        dst_cookie;           /*    28     4 */
	struct flowi               fl;                   /*    32    64 */
	/* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */
	union sctp_addr            ipaddr;               /*    96    28 */

Signed-off-by: Fan Du <redacted>
---
 include/net/sctp/structs.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index c0f4e29..d9c93a7 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h

@@ -782,6 +782,7 @@ struct sctp_transport {
 
 	/* Has this transport moved the ctsn since we last sacked */
 	__u32 sack_generation;
+	u32 dst_cookie;
 
 	struct flowi fl;
 

@@ -946,7 +947,6 @@ struct sctp_transport {
 	__u64 hb_nonce;
 
 	struct rcu_head rcu;
-	u32 dst_cookie;
 };
 
 struct sctp_transport *sctp_transport_new(struct net *, const union sctp_addr *,

-- 
1.7.9.5