Hi David,
This saves 8 bytes out of struct sock in 64bit arches, tested on x86_64.
[EMAIL PROTECTED] linux-2.6]$ codiff sock.o.before net/core/sock.o
/home/acme/git/linux-2.6/net/core/sock.c:
struct sock | -8
1 struct changed
[EMAIL PROTECTED] linux-2.6]$
Now struct sock has this layout, where we waste more 20 bytes, in four 4 byte
paddings in struct skb_buff_head members (layout at the bottom) + one 4 bytes
hole:
[EMAIL PROTECTED] linux-2.6]$ pahole -C sock net/core/sock.o
struct sock {
struct sock_common __sk_common; /* 0 56 */
unsigned char sk_shutdown:2; /* 56 1 */
unsigned char sk_no_check:2; /* 56 1 */
unsigned char sk_userlocks:4; /* 56 1 */
unsigned char sk_protocol; /* 57 1 */
short unsigned int sk_type; /* 58 2 */
int sk_rcvbuf; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
socket_lock_t sk_lock; /* 64 40 */
struct {
struct sk_buff * head; /* 104 8 */
struct sk_buff * tail; /* 112 8 */
} sk_backlog; /* 104 16 */
wait_queue_head_t * sk_sleep; /* 120 8 */
/* --- cacheline 2 boundary (128 bytes) --- */
struct dst_entry * sk_dst_cache; /* 128 8 */
struct xfrm_policy * sk_policy[2]; /* 136 16 */
rwlock_t sk_dst_lock; /* 152 8 */
atomic_t sk_rmem_alloc; /* 160 4 */
atomic_t sk_wmem_alloc; /* 164 4 */
atomic_t sk_omem_alloc; /* 168 4 */
int sk_sndbuf; /* 172 4 */
struct sk_buff_head sk_receive_queue; /* 176 32 */
/* XXX last struct has 4 bytes of padding */
/* --- cacheline 3 boundary (192 bytes) was 16 bytes ago --- */
struct sk_buff_head sk_write_queue; /* 208 32 */
/* XXX last struct has 4 bytes of padding */
struct sk_buff_head sk_async_wait_queue; /* 240 32 */
/* XXX last struct has 4 bytes of padding */
/* --- cacheline 4 boundary (256 bytes) was 16 bytes ago --- */
int sk_wmem_queued; /* 272 4 */
int sk_forward_alloc; /* 276 4 */
gfp_t sk_allocation; /* 280 4 */
int sk_route_caps; /* 284 4 */
int sk_gso_type; /* 288 4 */
int sk_rcvlowat; /* 292 4 */
long unsigned int sk_flags; /* 296 8 */
long unsigned int sk_lingertime; /* 304 8 */
struct sk_buff_head sk_error_queue; /* 312 32 */
/* XXX last struct has 4 bytes of padding */
/* --- cacheline 5 boundary (320 bytes) was 24 bytes ago --- */
struct proto * sk_prot_creator; /* 344 8 */
rwlock_t sk_callback_lock; /* 352 8 */
int sk_err; /* 360 4 */
int sk_err_soft; /* 364 4 */
short unsigned int sk_ack_backlog; /* 368 2 */
short unsigned int sk_max_ack_backlog; /* 370 2 */
__u32 sk_priority; /* 372 4 */
struct ucred sk_peercred; /* 376 12 */
/* XXX 4 bytes hole, try to pack */
/* --- cacheline 6 boundary (384 bytes) was 8 bytes ago --- */
long int sk_rcvtimeo; /* 392 8 */
long int sk_sndtimeo; /* 400 8 */
struct sk_filter * sk_filter; /* 408 8 */
void * sk_protinfo; /* 416 8 */
struct timer_list sk_timer; /* 424 48 */
/* --- cacheline 7 boundary (448 bytes) was 24 bytes ago --- */
ktime_t sk_stamp; /* 472 8 */
struct socket * sk_socket; /* 480 8 */
void * sk_user_data; /* 488 8 */
struct page * sk_sndmsg_page; /* 496 8 */
struct sk_buff * sk_send_head; /* 504 8 */
/* --- cacheline 8 boundary (512 bytes) --- */
__u32 sk_sndmsg_off; /* 512 4 */
int sk_write_pending; /* 516 4 */
void * sk_security; /* 520 8 */
void (*sk_state_change)(struct sock *); /* 528
8 */
void (*sk_data_ready)(struct sock *, int); /*
536 8 */
void (*sk_write_space)(struct sock *); /* 544
8 */
void (*sk_error_report)(struct sock *); /* 552
8 */
int (*sk_backlog_rcv)(struct sock *, struct
sk_buff *); /* 560 8 */
void (*sk_destruct)(struct sock *); /* 568
8 */
/* --- cacheline 9 boundary (576 bytes) --- */
}; /* size: 576, cachelines: 9 */
/* sum members: 572, holes: 1, sum holes: 4 */
/* paddings: 4, sum paddings: 16 */
[EMAIL PROTECTED] linux-2.6]$ pahole -C sk_buff_head net/core/sock.o
struct sk_buff_head {
struct sk_buff * next; /* 0 8 */
struct sk_buff * prev; /* 8 8 */
__u32 qlen; /* 16 4 */
spinlock_t lock; /* 20 8 */
}; /* size: 32, cachelines: 1 */
/* padding: 4 */
/* last cacheline: 32 bytes */
Signed-off-by: Arnaldo Carvalho de Melo <[EMAIL PROTECTED]>
---
diff --git a/include/net/sock.h b/include/net/sock.h
index 25c37e3..64a5429 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -218,13 +218,13 @@ struct sock {
atomic_t sk_rmem_alloc;
atomic_t sk_wmem_alloc;
atomic_t sk_omem_alloc;
+ int sk_sndbuf;
struct sk_buff_head sk_receive_queue;
struct sk_buff_head sk_write_queue;
struct sk_buff_head sk_async_wait_queue;
int sk_wmem_queued;
int sk_forward_alloc;
gfp_t sk_allocation;
- int sk_sndbuf;
int sk_route_caps;
int sk_gso_type;
int sk_rcvlowat;
-
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