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[TCP] H-TCP: Better time accounting 

Instead of estimating the time since the last congestion event, count
it directly.

Signed-off-by: Baruch Even <baruch@ev-en.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Baruch Even 2006-03-20 22:23:10 -08:00 committed by David S. Miller
parent 0bc6d90b82
commit 50bf3e224a
1 changed files with 26 additions and 18 deletions
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44
net/ipv4/tcp_htcp.c
View File

@ -27,13 +27,12 @@ struct htcp {
u16 alpha; /* Fixed point arith, << 7 */
u8 beta; /* Fixed point arith, << 7 */
u8 modeswitch; /* Delay modeswitch until we had at least one congestion event */
u8 ccount; /* Number of RTTs since last congestion event */
u8 undo_ccount;
u32 last_cong; /* Time since last congestion event end */
u32 undo_last_cong;
u16 pkts_acked;
u32 packetcount;
u32 minRTT;
u32 maxRTT;
u32 snd_cwnd_cnt2;
u32 undo_maxRTT;
u32 undo_old_maxB;
@ -46,21 +45,30 @@ struct htcp {
u32 lasttime;
};
static inline u32 htcp_cong_time(struct htcp *ca)
{
return jiffies - ca->last_cong;
}
static inline u32 htcp_ccount(struct htcp *ca)
{
return htcp_cong_time(ca)/ca->minRTT;
}
static inline void htcp_reset(struct htcp *ca)
{
ca->undo_ccount = ca->ccount;
ca->undo_last_cong = ca->last_cong;
ca->undo_maxRTT = ca->maxRTT;
ca->undo_old_maxB = ca->old_maxB;
ca->ccount = 0;
ca->snd_cwnd_cnt2 = 0;
ca->last_cong = jiffies;
}
static u32 htcp_cwnd_undo(struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
struct htcp *ca = inet_csk_ca(sk);
ca->ccount = ca->undo_ccount;
ca->last_cong = ca->undo_last_cong;
ca->maxRTT = ca->undo_maxRTT;
ca->old_maxB = ca->undo_old_maxB;
return max(tp->snd_cwnd, (tp->snd_ssthresh<<7)/ca->beta);
@ -78,7 +86,7 @@ static inline void measure_rtt(struct sock *sk)
ca->minRTT = srtt;
/* max RTT */
if (icsk->icsk_ca_state == TCP_CA_Open && tp->snd_ssthresh < 0xFFFF && ca->ccount > 3) {
if (icsk->icsk_ca_state == TCP_CA_Open && tp->snd_ssthresh < 0xFFFF && htcp_ccount(ca) > 3) {
if (ca->maxRTT < ca->minRTT)
ca->maxRTT = ca->minRTT;
if (ca->maxRTT < srtt && srtt <= ca->maxRTT+msecs_to_jiffies(20))
@ -113,7 +121,7 @@ static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked)
&& now - ca->lasttime >= ca->minRTT
&& ca->minRTT > 0) {
__u32 cur_Bi = ca->packetcount*HZ/(now - ca->lasttime);
if (ca->ccount <= 3) {
if (htcp_ccount(ca) <= 3) {
/* just after backoff */
ca->minB = ca->maxB = ca->Bi = cur_Bi;
} else {
@ -158,7 +166,7 @@ static inline void htcp_alpha_update(struct htcp *ca)
{
u32 minRTT = ca->minRTT;
u32 factor = 1;
u32 diff = ca->ccount * minRTT; /* time since last backoff */
u32 diff = htcp_cong_time(ca);
if (diff > HZ) {
diff -= HZ;
@ -223,14 +231,6 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
measure_rtt(sk);
/* keep track of number of round-trip times since last backoff event */
if (ca->snd_cwnd_cnt2 >= tp->snd_cwnd) {
ca->ccount++;
ca->snd_cwnd_cnt2 -= tp->snd_cwnd;
htcp_alpha_update(ca);
} else
ca->snd_cwnd_cnt2 += ca->pkts_acked;
/* In dangerous area, increase slowly.
* In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd
*/
@ -238,6 +238,7 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
tp->snd_cwnd_cnt = 0;
htcp_alpha_update(ca);
} else
tp->snd_cwnd_cnt += ca->pkts_acked;
@ -261,11 +262,18 @@ static void htcp_init(struct sock *sk)
ca->alpha = ALPHA_BASE;
ca->beta = BETA_MIN;
ca->pkts_acked = 1;
ca->last_cong = jiffies;
}
static void htcp_state(struct sock *sk, u8 new_state)
{
switch (new_state) {
case TCP_CA_Open:
{
struct htcp *ca = inet_csk_ca(sk);
ca->last_cong = jiffies;
}
break;
case TCP_CA_CWR:
case TCP_CA_Recovery:
case TCP_CA_Loss: