Shuffle the fields just added by commits a7775e9550fa ("udp: support
traceroute in direction tap-socket") and 9725e7988837 ("udp_flow:
Don't discard packets that arrive between bind() and connect()").
On x86_64, as reported by pahole(1), before:
struct udp_flow {
struct flow_common f; /* 0 76 */
/* --- cacheline 1 boundary (64 bytes) was 12 bytes ago --- */
_Bool closed:1; /* 76: 0 1 */
/* XXX 7 bits hole, try to pack */
_Bool flush0; /* 77 1 */
_Bool flush1:1; /* 78: 0 1 */
/* XXX 7 bits hole, try to pack */
/* XXX 1 byte hole, try to pack */
time_t ts; /* 80 8 */
int s[2]; /* 88 8 */
uint8_t ttl[2]; /* 96 2 */
/* size: 104, cachelines: 2, members: 7 */
/* sum members: 95, holes: 1, sum holes: 1 */
/* sum bitfield members: 2 bits, bit holes: 2, sum bit holes: 14 bits */
/* padding: 6 */
/* last cacheline: 40 bytes */
};
and after:
struct udp_flow {
struct flow_common f; /* 0 76 */
/* --- cacheline 1 boundary (64 bytes) was 12 bytes ago --- */
uint8_t ttl[2]; /* 76 2 */
_Bool closed:1; /* 78: 0 1 */
_Bool flush0:1; /* 78: 1 1 */
_Bool flush1:1; /* 78: 2 1 */
/* XXX 5 bits hole, try to pack */
/* XXX 1 byte hole, try to pack */
time_t ts; /* 80 8 */
int s[2]; /* 88 8 */
/* size: 96, cachelines: 2, members: 7 */
/* sum members: 94, holes: 1, sum holes: 1 */
/* sum bitfield members: 3 bits, bit holes: 1, sum bit holes: 5 bits */
/* last cacheline: 32 bytes */
};
It doesn't matter much because anyway the typical storage for struct
udp_flow is given by union flow:
union flow {
struct flow_common f; /* 0 76 */
struct flow_free_cluster free; /* 0 84 */
struct tcp_tap_conn tcp; /* 0 120 */
struct tcp_splice_conn tcp_splice; /* 0 120 */
struct icmp_ping_flow ping; /* 0 96 */
struct udp_flow udp; /* 0 96 */
};
but it still improves data locality somewhat, so let me fix this up
now that commits are fresh.
Signed-off-by: Stefano Brivio