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Release 4.11 net/ipv4/tcp_lp.c

Directory: net/ipv4
/*
 * TCP Low Priority (TCP-LP)
 *
 * TCP Low Priority is a distributed algorithm whose goal is to utilize only
 *   the excess network bandwidth as compared to the ``fair share`` of
 *   bandwidth as targeted by TCP.
 *
 * As of 2.6.13, Linux supports pluggable congestion control algorithms.
 * Due to the limitation of the API, we take the following changes from
 * the original TCP-LP implementation:
 *   o We use newReno in most core CA handling. Only add some checking
 *     within cong_avoid.
 *   o Error correcting in remote HZ, therefore remote HZ will be keeped
 *     on checking and updating.
 *   o Handling calculation of One-Way-Delay (OWD) within rtt_sample, since
 *     OWD have a similar meaning as RTT. Also correct the buggy formular.
 *   o Handle reaction for Early Congestion Indication (ECI) within
 *     pkts_acked, as mentioned within pseudo code.
 *   o OWD is handled in relative format, where local time stamp will in
 *     tcp_time_stamp format.
 *
 * Original Author:
 *   Aleksandar Kuzmanovic <akuzma@northwestern.edu>
 * Available from:
 *   http://www.ece.rice.edu/~akuzma/Doc/akuzma/TCP-LP.pdf
 * Original implementation for 2.4.19:
 *   http://www-ece.rice.edu/networks/TCP-LP/
 *
 * 2.6.x module Authors:
 *   Wong Hoi Sing, Edison <hswong3i@gmail.com>
 *   Hung Hing Lun, Mike <hlhung3i@gmail.com>
 * SourceForge project page:
 *   http://tcp-lp-mod.sourceforge.net/
 */

#include <linux/module.h>
#include <net/tcp.h>

/* resolution of owd */

#define LP_RESOL       1000

/**
 * enum tcp_lp_state
 * @LP_VALID_RHZ: is remote HZ valid?
 * @LP_VALID_OWD: is OWD valid?
 * @LP_WITHIN_THR: are we within threshold?
 * @LP_WITHIN_INF: are we within inference?
 *
 * TCP-LP's state flags.
 * We create this set of state flag mainly for debugging.
 */

enum tcp_lp_state {
	
LP_VALID_RHZ = (1 << 0),
	
LP_VALID_OWD = (1 << 1),
	
LP_WITHIN_THR = (1 << 3),
	
LP_WITHIN_INF = (1 << 4),
};

/**
 * struct lp
 * @flag: TCP-LP state flag
 * @sowd: smoothed OWD << 3
 * @owd_min: min OWD
 * @owd_max: max OWD
 * @owd_max_rsv: resrved max owd
 * @remote_hz: estimated remote HZ
 * @remote_ref_time: remote reference time
 * @local_ref_time: local reference time
 * @last_drop: time for last active drop
 * @inference: current inference
 *
 * TCP-LP's private struct.
 * We get the idea from original TCP-LP implementation where only left those we
 * found are really useful.
 */

struct lp {
	
u32 flag;
	
u32 sowd;
	
u32 owd_min;
	
u32 owd_max;
	
u32 owd_max_rsv;
	
u32 remote_hz;
	
u32 remote_ref_time;
	
u32 local_ref_time;
	
u32 last_drop;
	
u32 inference;
};

/**
 * tcp_lp_init
 *
 * Init all required variables.
 * Clone the handling from Vegas module implementation.
 */

static void tcp_lp_init(struct sock *sk) { struct lp *lp = inet_csk_ca(sk); lp->flag = 0; lp->sowd = 0; lp->owd_min = 0xffffffff; lp->owd_max = 0; lp->owd_max_rsv = 0; lp->remote_hz = 0; lp->remote_ref_time = 0; lp->local_ref_time = 0; lp->last_drop = 0; lp->inference = 0; }

Contributors

PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison81100.00%1100.00%
Total81100.00%1100.00%

/** * tcp_lp_cong_avoid * * Implementation of cong_avoid. * Will only call newReno CA when away from inference. * From TCP-LP's paper, this will be handled in additive increasement. */
static void tcp_lp_cong_avoid(struct sock *sk, u32 ack, u32 acked) { struct lp *lp = inet_csk_ca(sk); if (!(lp->flag & LP_WITHIN_INF)) tcp_reno_cong_avoid(sk, ack, acked); }

Contributors

PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison4595.74%150.00%
Yuchung Cheng24.26%150.00%
Total47100.00%2100.00%

/** * tcp_lp_remote_hz_estimator * * Estimate remote HZ. * We keep on updating the estimated value, where original TCP-LP * implementation only guest it for once and use forever. */
static u32 tcp_lp_remote_hz_estimator(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); struct lp *lp = inet_csk_ca(sk); s64 rhz = lp->remote_hz << 6; /* remote HZ << 6 */ s64 m = 0; /* not yet record reference time * go away!! record it before come back!! */ if (lp->remote_ref_time == 0 || lp->local_ref_time == 0) goto out; /* we can't calc remote HZ with no different!! */ if (tp->rx_opt.rcv_tsval == lp->remote_ref_time || tp->rx_opt.rcv_tsecr == lp->local_ref_time) goto out; m = HZ * (tp->rx_opt.rcv_tsval - lp->remote_ref_time) / (tp->rx_opt.rcv_tsecr - lp->local_ref_time); if (m < 0) m = -m; if (rhz > 0) { m -= rhz >> 6; /* m is now error in remote HZ est */ rhz += m; /* 63/64 old + 1/64 new */ } else rhz = m << 6; out: /* record time for successful remote HZ calc */ if ((rhz >> 6) > 0) lp->flag |= LP_VALID_RHZ; else lp->flag &= ~LP_VALID_RHZ; /* record reference time stamp */ lp->remote_ref_time = tp->rx_opt.rcv_tsval; lp->local_ref_time = tp->rx_opt.rcv_tsecr; return rhz >> 6; }

Contributors

PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison209100.00%3100.00%
Total209100.00%3100.00%

/** * tcp_lp_owd_calculator * * Calculate one way delay (in relative format). * Original implement OWD as minus of remote time difference to local time * difference directly. As this time difference just simply equal to RTT, when * the network status is stable, remote RTT will equal to local RTT, and result * OWD into zero. * It seems to be a bug and so we fixed it. */
static u32 tcp_lp_owd_calculator(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); struct lp *lp = inet_csk_ca(sk); s64 owd = 0; lp->remote_hz = tcp_lp_remote_hz_estimator(sk); if (lp->flag & LP_VALID_RHZ) { owd = tp->rx_opt.rcv_tsval * (LP_RESOL / lp->remote_hz) - tp->rx_opt.rcv_tsecr * (LP_RESOL / HZ); if (owd < 0) owd = -owd; } if (owd > 0) lp->flag |= LP_VALID_OWD; else lp->flag &= ~LP_VALID_OWD; return owd; }

Contributors

PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison117100.00%1100.00%
Total117100.00%1100.00%

/** * tcp_lp_rtt_sample * * Implementation or rtt_sample. * Will take the following action, * 1. calc OWD, * 2. record the min/max OWD, * 3. calc smoothed OWD (SOWD). * Most ideas come from the original TCP-LP implementation. */
static void tcp_lp_rtt_sample(struct sock *sk, u32 rtt) { struct lp *lp = inet_csk_ca(sk); s64 mowd = tcp_lp_owd_calculator(sk); /* sorry that we don't have valid data */ if (!(lp->flag & LP_VALID_RHZ) || !(lp->flag & LP_VALID_OWD)) return; /* record the next min owd */ if (mowd < lp->owd_min) lp->owd_min = mowd; /* always forget the max of the max * we just set owd_max as one below it */ if (mowd > lp->owd_max) { if (mowd > lp->owd_max_rsv) { if (lp->owd_max_rsv == 0) lp->owd_max = mowd; else lp->owd_max = lp->owd_max_rsv; lp->owd_max_rsv = mowd; } else lp->owd_max = mowd; } /* calc for smoothed owd */ if (lp->sowd != 0) { mowd -= lp->sowd >> 3; /* m is now error in owd est */ lp->sowd += mowd; /* owd = 7/8 owd + 1/8 new */ } else lp->sowd = mowd << 3; /* take the measured time be owd */ }

Contributors

PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison16299.39%150.00%
Stephen Hemminger10.61%150.00%
Total163100.00%2100.00%

/** * tcp_lp_pkts_acked * * Implementation of pkts_acked. * Deal with active drop under Early Congestion Indication. * Only drop to half and 1 will be handle, because we hope to use back * newReno in increase case. * We work it out by following the idea from TCP-LP's paper directly */
static void tcp_lp_pkts_acked(struct sock *sk, const struct ack_sample *sample) { struct tcp_sock *tp = tcp_sk(sk); struct lp *lp = inet_csk_ca(sk); if (sample->rtt_us > 0) tcp_lp_rtt_sample(sk, sample->rtt_us); /* calc inference */ if (tcp_time_stamp > tp->rx_opt.rcv_tsecr) lp->inference = 3 * (tcp_time_stamp - tp->rx_opt.rcv_tsecr); /* test if within inference */ if (lp->last_drop && (tcp_time_stamp - lp->last_drop < lp->inference)) lp->flag |= LP_WITHIN_INF; else lp->flag &= ~LP_WITHIN_INF; /* test if within threshold */ if (lp->sowd >> 3 < lp->owd_min + 15 * (lp->owd_max - lp->owd_min) / 100) lp->flag |= LP_WITHIN_THR; else lp->flag &= ~LP_WITHIN_THR; pr_debug("TCP-LP: %05o|%5u|%5u|%15u|%15u|%15u\n", lp->flag, tp->snd_cwnd, lp->remote_hz, lp->owd_min, lp->owd_max, lp->sowd >> 3); if (lp->flag & LP_WITHIN_THR) return; /* FIXME: try to reset owd_min and owd_max here * so decrease the chance the min/max is no longer suitable * and will usually within threshold when whithin inference */ lp->owd_min = lp->sowd >> 3; lp->owd_max = lp->sowd >> 2; lp->owd_max_rsv = lp->sowd >> 2; /* happened within inference * drop snd_cwnd into 1 */ if (lp->flag & LP_WITHIN_INF) tp->snd_cwnd = 1U; /* happened after inference * cut snd_cwnd into half */ else tp->snd_cwnd = max(tp->snd_cwnd >> 1U, 1U); /* record this drop time */ lp->last_drop = tcp_time_stamp; }

Contributors

PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison24391.70%120.00%
Stephen Hemminger103.77%240.00%
Lawrence Brakmo93.40%120.00%
Ilpo Järvinen31.13%120.00%
Total265100.00%5100.00%

static struct tcp_congestion_ops tcp_lp __read_mostly = { .init = tcp_lp_init, .ssthresh = tcp_reno_ssthresh, .undo_cwnd = tcp_reno_undo_cwnd, .cong_avoid = tcp_lp_cong_avoid, .pkts_acked = tcp_lp_pkts_acked, .owner = THIS_MODULE, .name = "lp" };
static int __init tcp_lp_register(void) { BUILD_BUG_ON(sizeof(struct lp) > ICSK_CA_PRIV_SIZE); return tcp_register_congestion_control(&tcp_lp); }

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PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison2696.30%150.00%
Alexey Dobriyan13.70%150.00%
Total27100.00%2100.00%


static void __exit tcp_lp_unregister(void) { tcp_unregister_congestion_control(&tcp_lp); }

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PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison15100.00%1100.00%
Total15100.00%1100.00%

module_init(tcp_lp_register); module_exit(tcp_lp_unregister); MODULE_AUTHOR("Wong Hoi Sing Edison, Hung Hing Lun Mike"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("TCP Low Priority");

Overall Contributors

PersonTokensPropCommitsCommitProp
Wong Hoi Sing Edison105096.95%325.00%
Stephen Hemminger121.11%325.00%
Lawrence Brakmo90.83%18.33%
Florian Westphal50.46%18.33%
Ilpo Järvinen30.28%18.33%
Yuchung Cheng20.18%18.33%
Lucas De Marchi10.09%18.33%
Alexey Dobriyan10.09%18.33%
Total1083100.00%12100.00%
Directory: net/ipv4
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