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tcp: fix stretch ACK bugs in Scalable

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Change Scalable to properly handle stretch ACKs in additive
increase mode by passing in the count of ACKed packets to
tcp_cong_avoid_ai().

In addition, because we are now precisely accounting for
stretch ACKs, including delayed ACKs, we can now change
TCP_SCALABLE_AI_CNT to 100.

Signed-off-by: Pengcheng Yang <yangpc@wangsu.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Pengcheng Yang 2020-03-16 14:35:08 +08:00 committed by David S. Miller
parent be0d935ebf
commit 5415e3c37a
1 changed files with 9 additions and 8 deletions
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17
net/ipv4/tcp_scalable.c
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@ -10,10 +10,9 @@
#include <net/tcp.h>
/* These factors derived from the recommended values in the aer:
* .01 and and 7/8. We use 50 instead of 100 to account for
* delayed ack.
* .01 and and 7/8.
*/
#define TCP_SCALABLE_AI_CNT 50U
#define TCP_SCALABLE_AI_CNT 100U
#define TCP_SCALABLE_MD_SCALE 3
static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
@ -23,11 +22,13 @@ static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
if (!tcp_is_cwnd_limited(sk))
return;
if (tcp_in_slow_start(tp))
tcp_slow_start(tp, acked);
else
tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
1);
if (tcp_in_slow_start(tp)) {
acked = tcp_slow_start(tp, acked);
if (!acked)
return;
}
tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
acked);
}
static u32 tcp_scalable_ssthresh(struct sock *sk)