From: Arnaldo Carvalho de Melo Date: Mon, 27 Nov 2006 19:58:59 +0000 (-0200) Subject: [XFRM]: Pack struct xfrm_policy X-Git-Tag: v2.6.20-rc1~34^2~40^2~137 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=46ca5f5dc4f1c9b5ac02c0090ae8ff4ac8560446;p=linux-2.6 [XFRM]: Pack struct xfrm_policy [acme@newtoy net-2.6.20]$ pahole net/ipv4/tcp.o xfrm_policy /* /pub/scm/linux/kernel/git/acme/net-2.6.20/include/linux/security.h:67 */ struct xfrm_policy { struct xfrm_policy * next; /* 0 4 */ struct hlist_node bydst; /* 4 8 */ struct hlist_node byidx; /* 12 8 */ rwlock_t lock; /* 20 36 */ atomic_t refcnt; /* 56 4 */ struct timer_list timer; /* 60 24 */ u8 type; /* 84 1 */ /* XXX 3 bytes hole, try to pack */ u32 priority; /* 88 4 */ u32 index; /* 92 4 */ struct xfrm_selector selector; /* 96 56 */ struct xfrm_lifetime_cfg lft; /* 152 64 */ struct xfrm_lifetime_cur curlft; /* 216 32 */ struct dst_entry * bundles; /* 248 4 */ __u16 family; /* 252 2 */ __u8 action; /* 254 1 */ __u8 flags; /* 255 1 */ __u8 dead; /* 256 1 */ __u8 xfrm_nr; /* 257 1 */ /* XXX 2 bytes hole, try to pack */ struct xfrm_sec_ctx * security; /* 260 4 */ struct xfrm_tmpl xfrm_vec[6]; /* 264 360 */ }; /* size: 624, sum members: 619, holes: 2, sum holes: 5 */ So lets have just one hole instead of two, by moving 'type' to just before 'action', end result: [acme@newtoy net-2.6.20]$ codiff -s /tmp/tcp.o.before net/ipv4/tcp.o /pub/scm/linux/kernel/git/acme/net-2.6.20/net/ipv4/tcp.c: struct xfrm_policy | -4 1 struct changed [acme@newtoy net-2.6.20]$ [acme@newtoy net-2.6.20]$ pahole -c 64 net/ipv4/tcp.o xfrm_policy /* /pub/scm/linux/kernel/git/acme/net-2.6.20/include/linux/security.h:67 */ struct xfrm_policy { struct xfrm_policy * next; /* 0 4 */ struct hlist_node bydst; /* 4 8 */ struct hlist_node byidx; /* 12 8 */ rwlock_t lock; /* 20 36 */ atomic_t refcnt; /* 56 4 */ struct timer_list timer; /* 60 24 */ u32 priority; /* 84 4 */ u32 index; /* 88 4 */ struct xfrm_selector selector; /* 92 56 */ struct xfrm_lifetime_cfg lft; /* 148 64 */ struct xfrm_lifetime_cur curlft; /* 212 32 */ struct dst_entry * bundles; /* 244 4 */ u16 family; /* 248 2 */ u8 type; /* 250 1 */ u8 action; /* 251 1 */ u8 flags; /* 252 1 */ u8 dead; /* 253 1 */ u8 xfrm_nr; /* 254 1 */ /* XXX 1 byte hole, try to pack */ struct xfrm_sec_ctx * security; /* 256 4 */ struct xfrm_tmpl xfrm_vec[6]; /* 260 360 */ }; /* size: 620, sum members: 619, holes: 1, sum holes: 1 */ Are there any fugly data dependencies here? None that I know. In the process changed the removed the __ prefixed types, that are just for userspace visible headers. Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/include/net/xfrm.h b/include/net/xfrm.h index 3878a88ff6..984e5c4526 100644 --- a/include/net/xfrm.h +++ b/include/net/xfrm.h @@ -340,18 +340,19 @@ struct xfrm_policy atomic_t refcnt; struct timer_list timer; - u8 type; u32 priority; u32 index; struct xfrm_selector selector; struct xfrm_lifetime_cfg lft; struct xfrm_lifetime_cur curlft; struct dst_entry *bundles; - __u16 family; - __u8 action; - __u8 flags; - __u8 dead; - __u8 xfrm_nr; + u16 family; + u8 type; + u8 action; + u8 flags; + u8 dead; + u8 xfrm_nr; + /* XXX 1 byte hole, try to pack */ struct xfrm_sec_ctx *security; struct xfrm_tmpl xfrm_vec[XFRM_MAX_DEPTH]; };