[PATCH net-next] netfilter: Reorder fields in 'struct nf_conntrack_expect'

[Christophe JAILLET]

Group some variables based on their sizes to reduce holes.
On x86_64, this shrinks the size of 'struct nf_conntrack_expect' from 264
to 256 bytes.

This structure deserve a dedicated cache, so reducing its size looks nice.

Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
Using pahole

Before:
======
struct nf_conntrack_expect {
	struct hlist_node          lnode;                /*     0    16 */
	struct hlist_node          hnode;                /*    16    16 */
	struct nf_conntrack_tuple  tuple;                /*    32    40 */
	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
	struct nf_conntrack_tuple_mask mask;             /*    72    20 */

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

	void                       (*expectfn)(struct nf_conn *, struct nf_conntrack_expect *); /*    96     8 */
	struct nf_conntrack_helper * helper;             /*   104     8 */
	struct nf_conn *           master;               /*   112     8 */
	struct timer_list          timeout;              /*   120    88 */
	/* --- cacheline 3 boundary (192 bytes) was 16 bytes ago --- */
	refcount_t                 use;                  /*   208     4 */
	unsigned int               flags;                /*   212     4 */
	unsigned int               class;                /*   216     4 */
	union nf_inet_addr         saved_addr;           /*   220    16 */
	union nf_conntrack_man_proto saved_proto;        /*   236     2 */

	/* XXX 2 bytes hole, try to pack */

	enum ip_conntrack_dir      dir;                  /*   240     4 */

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

	struct callback_head       rcu __attribute__((__aligned__(8))); /*   248    16 */

	/* size: 264, cachelines: 5, members: 15 */
	/* sum members: 254, holes: 3, sum holes: 10 */
	/* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
	/* last cacheline: 8 bytes */
} __attribute__((__aligned__(8)));


After:
=====
struct nf_conntrack_expect {
	struct hlist_node          lnode;                /*     0    16 */
	struct hlist_node          hnode;                /*    16    16 */
	struct nf_conntrack_tuple  tuple;                /*    32    40 */
	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
	struct nf_conntrack_tuple_mask mask;             /*    72    20 */
	refcount_t                 use;                  /*    92     4 */
	unsigned int               flags;                /*    96     4 */
	unsigned int               class;                /*   100     4 */
	void                       (*expectfn)(struct nf_conn *, struct nf_conntrack_expect *); /*   104     8 */
	struct nf_conntrack_helper * helper;             /*   112     8 */
	struct nf_conn *           master;               /*   120     8 */
	/* --- cacheline 2 boundary (128 bytes) --- */
	struct timer_list          timeout;              /*   128    88 */
	/* --- cacheline 3 boundary (192 bytes) was 24 bytes ago --- */
	union nf_inet_addr         saved_addr;           /*   216    16 */
	union nf_conntrack_man_proto saved_proto;        /*   232     2 */

	/* XXX 2 bytes hole, try to pack */

	enum ip_conntrack_dir      dir;                  /*   236     4 */
	struct callback_head       rcu __attribute__((__aligned__(8))); /*   240    16 */

	/* size: 256, cachelines: 4, members: 15 */
	/* sum members: 254, holes: 1, sum holes: 2 */
	/* forced alignments: 1 */
} __attribute__((__aligned__(8)));
---
 include/net/netfilter/nf_conntrack_expect.h | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_expect.h b/include/net/netfilter/nf_conntrack_expect.h
index 0855b60fba17..cf0d81be5a96 100644
--- a/include/net/netfilter/nf_conntrack_expect.h
+++ b/include/net/netfilter/nf_conntrack_expect.h
@@ -26,6 +26,15 @@ struct nf_conntrack_expect {
 	struct nf_conntrack_tuple tuple;
 	struct nf_conntrack_tuple_mask mask;
 
+	/* Usage count. */
+	refcount_t use;
+
+	/* Flags */
+	unsigned int flags;
+
+	/* Expectation class */
+	unsigned int class;
+
 	/* Function to call after setup and insertion */
 	void (*expectfn)(struct nf_conn *new,
 			 struct nf_conntrack_expect *this);
@@ -39,15 +48,6 @@ struct nf_conntrack_expect {
 	/* Timer function; deletes the expectation. */
 	struct timer_list timeout;
 
-	/* Usage count. */
-	refcount_t use;
-
-	/* Flags */
-	unsigned int flags;
-
-	/* Expectation class */
-	unsigned int class;
-
 #if IS_ENABLED(CONFIG_NF_NAT)
 	union nf_inet_addr saved_addr;
 	/* This is the original per-proto part, used to map the
-- 
2.34.1