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tcp: simplify tcp_current_mss
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There's very little need for most of the callsites to get
tp->xmit_goal_size updated. That will cost us divide as is,
so slice the function in two. Also, the only users of the
tp->xmit_goal_size are directly behind tcp_current_mss(),
so there's no need to store that variable into tcp_sock
at all! The drop of xmit_goal_size currently leaves 16-bit
hole and some reorganization would again be necessary to
change that (but I'm aiming to fill that hole with u16
xmit_goal_size_segs to cache the results of the remaining
divide to get that tso on regression).

Bring xmit_goal_size parts into tcp.c

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Ilpo Järvinen authored and David S. Miller committed Mar 16, 2009
1 parent 72211e9 commit 0c54b85
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Showing 5 changed files with 54 additions and 46 deletions.
1 change: 0 additions & 1 deletion include/linux/tcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -248,7 +248,6 @@ struct tcp_sock {
/* inet_connection_sock has to be the first member of tcp_sock */
struct inet_connection_sock inet_conn;
u16 tcp_header_len; /* Bytes of tcp header to send */
u16 xmit_size_goal; /* Goal for segmenting output packets */

/*
* Header prediction flags
Expand Down
13 changes: 11 additions & 2 deletions include/net/tcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -481,7 +481,16 @@ static inline void tcp_clear_xmit_timers(struct sock *sk)
}

extern unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
extern unsigned int tcp_current_mss(struct sock *sk, int large);
extern unsigned int tcp_current_mss(struct sock *sk);

/* Bound MSS / TSO packet size with the half of the window */
static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
{
if (tp->max_window && pktsize > (tp->max_window >> 1))
return max(tp->max_window >> 1, 68U - tp->tcp_header_len);
else
return pktsize;
}

/* tcp.c */
extern void tcp_get_info(struct sock *, struct tcp_info *);
Expand Down Expand Up @@ -822,7 +831,7 @@ static inline void tcp_push_pending_frames(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);

__tcp_push_pending_frames(sk, tcp_current_mss(sk, 1), tp->nonagle);
__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
}

static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
Expand Down
43 changes: 35 additions & 8 deletions net/ipv4/tcp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -661,6 +661,37 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp)
return NULL;
}

static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
int large_allowed)
{
struct tcp_sock *tp = tcp_sk(sk);
u32 xmit_size_goal;

xmit_size_goal = mss_now;

if (large_allowed && sk_can_gso(sk)) {
xmit_size_goal = ((sk->sk_gso_max_size - 1) -
inet_csk(sk)->icsk_af_ops->net_header_len -
inet_csk(sk)->icsk_ext_hdr_len -
tp->tcp_header_len);

xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal);
xmit_size_goal -= (xmit_size_goal % mss_now);
}

return xmit_size_goal;
}

static int tcp_send_mss(struct sock *sk, int *size_goal, int flags)
{
int mss_now;

mss_now = tcp_current_mss(sk);
*size_goal = tcp_xmit_size_goal(sk, mss_now, !(flags & MSG_OOB));

return mss_now;
}

static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffset,
size_t psize, int flags)
{
Expand All @@ -677,8 +708,7 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffse

clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);

mss_now = tcp_current_mss(sk, !(flags&MSG_OOB));
size_goal = tp->xmit_size_goal;
mss_now = tcp_send_mss(sk, &size_goal, flags);
copied = 0;

err = -EPIPE;
Expand Down Expand Up @@ -761,8 +791,7 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffse
if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
goto do_error;

mss_now = tcp_current_mss(sk, !(flags&MSG_OOB));
size_goal = tp->xmit_size_goal;
mss_now = tcp_send_mss(sk, &size_goal, flags);
}

out:
Expand Down Expand Up @@ -844,8 +873,7 @@ int tcp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
/* This should be in poll */
clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);

mss_now = tcp_current_mss(sk, !(flags&MSG_OOB));
size_goal = tp->xmit_size_goal;
mss_now = tcp_send_mss(sk, &size_goal, flags);

/* Ok commence sending. */
iovlen = msg->msg_iovlen;
Expand Down Expand Up @@ -1007,8 +1035,7 @@ int tcp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
goto do_error;

mss_now = tcp_current_mss(sk, !(flags&MSG_OOB));
size_goal = tp->xmit_size_goal;
mss_now = tcp_send_mss(sk, &size_goal, flags);
}
}

Expand Down
2 changes: 1 addition & 1 deletion net/ipv4/tcp_input.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2864,7 +2864,7 @@ void tcp_simple_retransmit(struct sock *sk)
const struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb;
unsigned int mss = tcp_current_mss(sk, 0);
unsigned int mss = tcp_current_mss(sk);
u32 prior_lost = tp->lost_out;

tcp_for_write_queue(skb, sk) {
Expand Down
41 changes: 7 additions & 34 deletions net/ipv4/tcp_output.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -921,7 +921,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
* factor and mss.
*/
if (tcp_skb_pcount(skb) > 1)
tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1));
tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk));

return 0;
}
Expand Down Expand Up @@ -982,15 +982,6 @@ void tcp_mtup_init(struct sock *sk)
icsk->icsk_mtup.probe_size = 0;
}

/* Bound MSS / TSO packet size with the half of the window */
static int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
{
if (tp->max_window && pktsize > (tp->max_window >> 1))
return max(tp->max_window >> 1, 68U - tp->tcp_header_len);
else
return pktsize;
}

/* This function synchronize snd mss to current pmtu/exthdr set.
tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
Expand Down Expand Up @@ -1037,22 +1028,17 @@ unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
/* Compute the current effective MSS, taking SACKs and IP options,
* and even PMTU discovery events into account.
*/
unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
unsigned int tcp_current_mss(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
struct dst_entry *dst = __sk_dst_get(sk);
u32 mss_now;
u16 xmit_size_goal;
int doing_tso = 0;
unsigned header_len;
struct tcp_out_options opts;
struct tcp_md5sig_key *md5;

mss_now = tp->mss_cache;

if (large_allowed && sk_can_gso(sk))
doing_tso = 1;

if (dst) {
u32 mtu = dst_mtu(dst);
if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
Expand All @@ -1070,19 +1056,6 @@ unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
mss_now -= delta;
}

xmit_size_goal = mss_now;

if (doing_tso) {
xmit_size_goal = ((sk->sk_gso_max_size - 1) -
inet_csk(sk)->icsk_af_ops->net_header_len -
inet_csk(sk)->icsk_ext_hdr_len -
tp->tcp_header_len);

xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal);
xmit_size_goal -= (xmit_size_goal % mss_now);
}
tp->xmit_size_goal = xmit_size_goal;

return mss_now;
}

Expand Down Expand Up @@ -1264,7 +1237,7 @@ int tcp_may_send_now(struct sock *sk)
struct sk_buff *skb = tcp_send_head(sk);

return (skb &&
tcp_snd_test(sk, skb, tcp_current_mss(sk, 1),
tcp_snd_test(sk, skb, tcp_current_mss(sk),
(tcp_skb_is_last(sk, skb) ?
tp->nonagle : TCP_NAGLE_PUSH)));
}
Expand Down Expand Up @@ -1421,7 +1394,7 @@ static int tcp_mtu_probe(struct sock *sk)
return -1;

/* Very simple search strategy: just double the MSS. */
mss_now = tcp_current_mss(sk, 0);
mss_now = tcp_current_mss(sk);
probe_size = 2 * tp->mss_cache;
size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
Expand Down Expand Up @@ -1903,7 +1876,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
return -EHOSTUNREACH; /* Routing failure or similar. */

cur_mss = tcp_current_mss(sk, 0);
cur_mss = tcp_current_mss(sk);

/* If receiver has shrunk his window, and skb is out of
* new window, do not retransmit it. The exception is the
Expand Down Expand Up @@ -2111,7 +2084,7 @@ void tcp_send_fin(struct sock *sk)
* unsent frames. But be careful about outgoing SACKS
* and IP options.
*/
mss_now = tcp_current_mss(sk, 1);
mss_now = tcp_current_mss(sk);

if (tcp_send_head(sk) != NULL) {
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN;
Expand Down Expand Up @@ -2523,7 +2496,7 @@ int tcp_write_wakeup(struct sock *sk)
if ((skb = tcp_send_head(sk)) != NULL &&
before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
int err;
unsigned int mss = tcp_current_mss(sk, 0);
unsigned int mss = tcp_current_mss(sk);
unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;

if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
Expand Down

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