f4805eded7
TCP peformance with TSO over networks with delay is awful. On a 100Mbit link with 150ms delay, we get 4Mbits/sec with TSO and 50Mbits/sec without TSO. The problem is with TSO, we intentionally do not keep the maximum number of packets in flight to fill the window, we hold out to until we can send a MSS chunk. But, we also don't update the congestion window unless we have filled, as per RFC2861. This patch replaces the check for the congestion window being full with something smarter that accounts for TSO. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
72 lines
1.6 KiB
C
72 lines
1.6 KiB
C
/* Tom Kelly's Scalable TCP
|
|
*
|
|
* See htt://www-lce.eng.cam.ac.uk/~ctk21/scalable/
|
|
*
|
|
* John Heffner <jheffner@sc.edu>
|
|
*/
|
|
|
|
#include <linux/config.h>
|
|
#include <linux/module.h>
|
|
#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.
|
|
*/
|
|
#define TCP_SCALABLE_AI_CNT 50U
|
|
#define TCP_SCALABLE_MD_SCALE 3
|
|
|
|
static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
|
|
u32 in_flight, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (!tcp_is_cwnd_limited(sk, in_flight))
|
|
return;
|
|
|
|
if (tp->snd_cwnd <= tp->snd_ssthresh) {
|
|
tp->snd_cwnd++;
|
|
} else {
|
|
tp->snd_cwnd_cnt++;
|
|
if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
|
|
tp->snd_cwnd++;
|
|
tp->snd_cwnd_cnt = 0;
|
|
}
|
|
}
|
|
tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
static u32 tcp_scalable_ssthresh(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
|
|
}
|
|
|
|
|
|
static struct tcp_congestion_ops tcp_scalable = {
|
|
.ssthresh = tcp_scalable_ssthresh,
|
|
.cong_avoid = tcp_scalable_cong_avoid,
|
|
.min_cwnd = tcp_reno_min_cwnd,
|
|
|
|
.owner = THIS_MODULE,
|
|
.name = "scalable",
|
|
};
|
|
|
|
static int __init tcp_scalable_register(void)
|
|
{
|
|
return tcp_register_congestion_control(&tcp_scalable);
|
|
}
|
|
|
|
static void __exit tcp_scalable_unregister(void)
|
|
{
|
|
tcp_unregister_congestion_control(&tcp_scalable);
|
|
}
|
|
|
|
module_init(tcp_scalable_register);
|
|
module_exit(tcp_scalable_unregister);
|
|
|
|
MODULE_AUTHOR("John Heffner");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("Scalable TCP");
|