[TCP]: Appropriate Byte Count support

This is an updated version of the RFC3465 ABC patch originally
for Linux 2.6.11-rc4 by Yee-Ting Li. ABC is a way of counting
bytes ack'd rather than packets when updating congestion control.

The orignal ABC described in the RFC applied to a Reno style
algorithm. For advanced congestion control there is little
change after leaving slow start.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger 2005-11-10 17:09:53 -08:00 committed by David S. Miller
parent 7faffa1c7f
commit 9772efb970
9 changed files with 63 additions and 11 deletions

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@ -78,6 +78,11 @@ inet_peer_gc_maxtime - INTEGER
TCP variables:
tcp_abc - INTEGER
Controls Appropriate Byte Count defined in RFC3465. If set to
0 then does congestion avoid once per ack. 1 is conservative
value, and 2 is more agressive.
tcp_syn_retries - INTEGER
Number of times initial SYNs for an active TCP connection attempt
will be retransmitted. Should not be higher than 255. Default value

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@ -390,6 +390,7 @@ enum
NET_TCP_BIC_BETA=108,
NET_IPV4_ICMP_ERRORS_USE_INBOUND_IFADDR=109,
NET_TCP_CONG_CONTROL=110,
NET_TCP_ABC=111,
};
enum {

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@ -326,6 +326,7 @@ struct tcp_sock {
__u32 snd_up; /* Urgent pointer */
__u32 total_retrans; /* Total retransmits for entire connection */
__u32 bytes_acked; /* Appropriate Byte Counting - RFC3465 */
unsigned int keepalive_time; /* time before keep alive takes place */
unsigned int keepalive_intvl; /* time interval between keep alive probes */

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@ -218,6 +218,7 @@ extern int sysctl_tcp_low_latency;
extern int sysctl_tcp_nometrics_save;
extern int sysctl_tcp_moderate_rcvbuf;
extern int sysctl_tcp_tso_win_divisor;
extern int sysctl_tcp_abc;
extern atomic_t tcp_memory_allocated;
extern atomic_t tcp_sockets_allocated;
@ -770,6 +771,23 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
*/
static inline void tcp_slow_start(struct tcp_sock *tp)
{
if (sysctl_tcp_abc) {
/* RFC3465: Slow Start
* TCP sender SHOULD increase cwnd by the number of
* previously unacknowledged bytes ACKed by each incoming
* acknowledgment, provided the increase is not more than L
*/
if (tp->bytes_acked < tp->mss_cache)
return;
/* We MAY increase by 2 if discovered delayed ack */
if (sysctl_tcp_abc > 1 && tp->bytes_acked > 2*tp->mss_cache) {
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
}
}
tp->bytes_acked = 0;
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
}
@ -804,6 +822,7 @@ static inline void tcp_enter_cwr(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);
tp->prior_ssthresh = 0;
tp->bytes_acked = 0;
if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
__tcp_enter_cwr(sk);
tcp_set_ca_state(sk, TCP_CA_CWR);

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@ -645,6 +645,14 @@ ctl_table ipv4_table[] = {
.proc_handler = &proc_tcp_congestion_control,
.strategy = &sysctl_tcp_congestion_control,
},
{
.ctl_name = NET_TCP_ABC,
.procname = "tcp_abc",
.data = &sysctl_tcp_abc,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{ .ctl_name = 0 }
};

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@ -1669,6 +1669,7 @@ int tcp_disconnect(struct sock *sk, int flags)
tp->packets_out = 0;
tp->snd_ssthresh = 0x7fffffff;
tp->snd_cwnd_cnt = 0;
tp->bytes_acked = 0;
tcp_set_ca_state(sk, TCP_CA_Open);
tcp_clear_retrans(tp);
inet_csk_delack_init(sk);

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@ -192,17 +192,26 @@ void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 rtt, u32 in_flight,
/* In "safe" area, increase. */
if (tp->snd_cwnd <= tp->snd_ssthresh)
tcp_slow_start(tp);
else {
/* In dangerous area, increase slowly.
* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
*/
if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
tp->snd_cwnd_cnt = 0;
} else
tp->snd_cwnd_cnt++;
}
/* In dangerous area, increase slowly. */
else if (sysctl_tcp_abc) {
/* RFC3465: Apppriate Byte Count
* increase once for each full cwnd acked
*/
if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
}
} else {
/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd */
if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
tp->snd_cwnd_cnt = 0;
} else
tp->snd_cwnd_cnt++;
}
}
EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);

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@ -89,6 +89,7 @@ int sysctl_tcp_frto;
int sysctl_tcp_nometrics_save;
int sysctl_tcp_moderate_rcvbuf = 1;
int sysctl_tcp_abc = 1;
#define FLAG_DATA 0x01 /* Incoming frame contained data. */
#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
@ -1247,6 +1248,7 @@ void tcp_enter_loss(struct sock *sk, int how)
tp->snd_cwnd_cnt = 0;
tp->snd_cwnd_stamp = tcp_time_stamp;
tp->bytes_acked = 0;
tcp_clear_retrans(tp);
/* Push undo marker, if it was plain RTO and nothing
@ -1904,6 +1906,7 @@ tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
TCP_ECN_queue_cwr(tp);
}
tp->bytes_acked = 0;
tp->snd_cwnd_cnt = 0;
tcp_set_ca_state(sk, TCP_CA_Recovery);
}
@ -2310,6 +2313,9 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
if (before(ack, prior_snd_una))
goto old_ack;
if (sysctl_tcp_abc && icsk->icsk_ca_state < TCP_CA_CWR)
tp->bytes_acked += ack - prior_snd_una;
if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
/* Window is constant, pure forward advance.
* No more checks are required.
@ -4370,6 +4376,7 @@ discard:
EXPORT_SYMBOL(sysctl_tcp_ecn);
EXPORT_SYMBOL(sysctl_tcp_reordering);
EXPORT_SYMBOL(sysctl_tcp_abc);
EXPORT_SYMBOL(tcp_parse_options);
EXPORT_SYMBOL(tcp_rcv_established);
EXPORT_SYMBOL(tcp_rcv_state_process);

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@ -380,6 +380,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
*/
newtp->snd_cwnd = 2;
newtp->snd_cwnd_cnt = 0;
newtp->bytes_acked = 0;
newtp->frto_counter = 0;
newtp->frto_highmark = 0;