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Release 4.11 net/ipv4/tcp_veno.c

Directory: net/ipv4
/*
 * TCP Veno congestion control
 *
 * This is based on the congestion detection/avoidance scheme described in
 *    C. P. Fu, S. C. Liew.
 *    "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks."
 *    IEEE Journal on Selected Areas in Communication,
 *    Feb. 2003.
 *      See http://www.ie.cuhk.edu.hk/fileadmin/staff_upload/soung/Journal/J3.pdf
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/inet_diag.h>

#include <net/tcp.h>

/* Default values of the Veno variables, in fixed-point representation
 * with V_PARAM_SHIFT bits to the right of the binary point.
 */

#define V_PARAM_SHIFT 1

static const int beta = 3 << V_PARAM_SHIFT;

/* Veno variables */

struct veno {
	
u8 doing_veno_now;	/* if true, do veno for this rtt */
	
u16 cntrtt;		/* # of rtts measured within last rtt */
	
u32 minrtt;		/* min of rtts measured within last rtt (in usec) */
	
u32 basertt;		/* the min of all Veno rtt measurements seen (in usec) */
	
u32 inc;		/* decide whether to increase cwnd */
	
u32 diff;		/* calculate the diff rate */
	
u32 loss_cwnd;		/* cwnd when loss occured */
};

/* There are several situations when we must "re-start" Veno:
 *
 *  o when a connection is established
 *  o after an RTO
 *  o after fast recovery
 *  o when we send a packet and there is no outstanding
 *    unacknowledged data (restarting an idle connection)
 *
 */

static inline void veno_enable(struct sock *sk) { struct veno *veno = inet_csk_ca(sk); /* turn on Veno */ veno->doing_veno_now = 1; veno->minrtt = 0x7fffffff; }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou35100.00%1100.00%
Total35100.00%1100.00%


static inline void veno_disable(struct sock *sk) { struct veno *veno = inet_csk_ca(sk); /* turn off Veno */ veno->doing_veno_now = 0; }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou29100.00%1100.00%
Total29100.00%1100.00%


static void tcp_veno_init(struct sock *sk) { struct veno *veno = inet_csk_ca(sk); veno->basertt = 0x7fffffff; veno->inc = 1; veno_enable(sk); }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou38100.00%1100.00%
Total38100.00%1100.00%

/* Do rtt sampling needed for Veno. */
static void tcp_veno_pkts_acked(struct sock *sk, const struct ack_sample *sample) { struct veno *veno = inet_csk_ca(sk); u32 vrtt; if (sample->rtt_us < 0) return; /* Never allow zero rtt or baseRTT */ vrtt = sample->rtt_us + 1; /* Filter to find propagation delay: */ if (vrtt < veno->basertt) veno->basertt = vrtt; /* Find the min rtt during the last rtt to find * the current prop. delay + queuing delay: */ veno->minrtt = min(veno->minrtt, vrtt); veno->cntrtt++; }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou5971.95%120.00%
Stephen Hemminger1012.20%240.00%
Lawrence Brakmo910.98%120.00%
Ilpo Järvinen44.88%120.00%
Total82100.00%5100.00%


static void tcp_veno_state(struct sock *sk, u8 ca_state) { if (ca_state == TCP_CA_Open) veno_enable(sk); else veno_disable(sk); }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou31100.00%1100.00%
Total31100.00%1100.00%

/* * If the connection is idle and we are restarting, * then we don't want to do any Veno calculations * until we get fresh rtt samples. So when we * restart, we reset our Veno state to a clean * state. After we get acks for this flight of * packets, _then_ we can make Veno calculations * again. */
static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event) { if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START) tcp_veno_init(sk); }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou30100.00%1100.00%
Total30100.00%1100.00%


static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked) { struct tcp_sock *tp = tcp_sk(sk); struct veno *veno = inet_csk_ca(sk); if (!veno->doing_veno_now) { tcp_reno_cong_avoid(sk, ack, acked); return; } /* limited by applications */ if (!tcp_is_cwnd_limited(sk)) return; /* We do the Veno calculations only if we got enough rtt samples */ if (veno->cntrtt <= 2) { /* We don't have enough rtt samples to do the Veno * calculation, so we'll behave like Reno. */ tcp_reno_cong_avoid(sk, ack, acked); } else { u64 target_cwnd; u32 rtt; /* We have enough rtt samples, so, using the Veno * algorithm, we determine the state of the network. */ rtt = veno->minrtt; target_cwnd = (u64)tp->snd_cwnd * veno->basertt; target_cwnd <<= V_PARAM_SHIFT; do_div(target_cwnd, rtt); veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd; if (tcp_in_slow_start(tp)) { /* Slow start. */ tcp_slow_start(tp, acked); } else { /* Congestion avoidance. */ if (veno->diff < beta) { /* In the "non-congestive state", increase cwnd * every rtt. */ tcp_cong_avoid_ai(tp, tp->snd_cwnd, 1); } else { /* In the "congestive state", increase cwnd * every other rtt. */ if (tp->snd_cwnd_cnt >= tp->snd_cwnd) { if (veno->inc && tp->snd_cwnd < tp->snd_cwnd_clamp) { tp->snd_cwnd++; veno->inc = 0; } else veno->inc = 1; tp->snd_cwnd_cnt = 0; } else tp->snd_cwnd_cnt++; } } if (tp->snd_cwnd < 2) tp->snd_cwnd = 2; else if (tp->snd_cwnd > tp->snd_cwnd_clamp) tp->snd_cwnd = tp->snd_cwnd_clamp; } /* Wipe the slate clean for the next rtt. */ /* veno->cntrtt = 0; */ veno->minrtt = 0x7fffffff; }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou25588.85%112.50%
Lachlan Andrew124.18%112.50%
Yuchung Cheng82.79%225.00%
Harvey Harrison41.39%112.50%
Ilpo Järvinen41.39%112.50%
Neal Cardwell20.70%112.50%
Christoph Paasch20.70%112.50%
Total287100.00%8100.00%

/* Veno MD phase */
static u32 tcp_veno_ssthresh(struct sock *sk) { const struct tcp_sock *tp = tcp_sk(sk); struct veno *veno = inet_csk_ca(sk); veno->loss_cwnd = tp->snd_cwnd; if (veno->diff < beta) /* in "non-congestive state", cut cwnd by 1/5 */ return max(tp->snd_cwnd * 4 / 5, 2U); else /* in "congestive state", cut cwnd by 1/2 */ return max(tp->snd_cwnd >> 1U, 2U); }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou6989.61%150.00%
Florian Westphal810.39%150.00%
Total77100.00%2100.00%


static u32 tcp_veno_cwnd_undo(struct sock *sk) { const struct veno *veno = inet_csk_ca(sk); return max(tcp_sk(sk)->snd_cwnd, veno->loss_cwnd); }

Contributors

PersonTokensPropCommitsCommitProp
Florian Westphal37100.00%1100.00%
Total37100.00%1100.00%

static struct tcp_congestion_ops tcp_veno __read_mostly = { .init = tcp_veno_init, .ssthresh = tcp_veno_ssthresh, .undo_cwnd = tcp_veno_cwnd_undo, .cong_avoid = tcp_veno_cong_avoid, .pkts_acked = tcp_veno_pkts_acked, .set_state = tcp_veno_state, .cwnd_event = tcp_veno_cwnd_event, .owner = THIS_MODULE, .name = "veno", };
static int __init tcp_veno_register(void) { BUILD_BUG_ON(sizeof(struct veno) > ICSK_CA_PRIV_SIZE); tcp_register_congestion_control(&tcp_veno); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou2896.55%150.00%
Alexey Dobriyan13.45%150.00%
Total29100.00%2100.00%


static void __exit tcp_veno_unregister(void) { tcp_unregister_congestion_control(&tcp_veno); }

Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou15100.00%1100.00%
Total15100.00%1100.00%

module_init(tcp_veno_register); module_exit(tcp_veno_unregister); MODULE_AUTHOR("Bin Zhou, Cheng Peng Fu"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("TCP Veno");

Overall Contributors

PersonTokensPropCommitsCommitProp
Bin Zhou72286.36%16.25%
Florian Westphal546.46%16.25%
Stephen Hemminger131.56%318.75%
Lachlan Andrew121.44%16.25%
Lawrence Brakmo91.08%16.25%
Ilpo Järvinen80.96%212.50%
Yuchung Cheng80.96%212.50%
Harvey Harrison40.48%16.25%
Neal Cardwell20.24%16.25%
Christoph Paasch20.24%16.25%
Justin P. Mattock10.12%16.25%
Alexey Dobriyan10.12%16.25%
Total836100.00%16100.00%
Directory: net/ipv4
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