Date: Tue, 1 Feb 2011 07:05:14 +0000 (UTC) From: Lawrence Stewart <lstewart@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r218155 - in head/sys: modules/cc modules/cc/cc_chd netinet/cc Message-ID: <201102010705.p1175EgG061905@svn.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: lstewart Date: Tue Feb 1 07:05:14 2011 New Revision: 218155 URL: http://svn.freebsd.org/changeset/base/218155 Log: Import an implementation of the CAIA-Hamilton-Delay (CHD) congestion control algorithm described in the paper "Improved coexistence and loss tolerance for delay based TCP congestion control" by Hayes and Armitage. It is implemented as a kernel module compatible with the recently committed modular congestion control framework. CHD enhances the approach taken by the Hamilton-Delay (HD) algorithm to provide tolerance to non-congestion related packet loss and improvements to coexistence with loss-based congestion control algorithms. A key idea in improving coexistence with loss-based congestion control algorithms is the use of a shadow window, which attempts to track how NewReno's congestion window (cwnd) would evolve. At the next packet loss congestion event, CHD uses the shadow window to correct cwnd in a way that reduces the amount of unfairness CHD experiences when competing with loss-based algorithms. In collaboration with: David Hayes <dahayes at swin edu au> and Grenville Armitage <garmitage at swin edu au> Sponsored by: FreeBSD Foundation Reviewed by: bz and others along the way MFC after: 3 months Added: head/sys/modules/cc/cc_chd/ head/sys/modules/cc/cc_chd/Makefile (contents, props changed) head/sys/netinet/cc/cc_chd.c (contents, props changed) Modified: head/sys/modules/cc/Makefile Modified: head/sys/modules/cc/Makefile ============================================================================== --- head/sys/modules/cc/Makefile Tue Feb 1 06:59:44 2011 (r218154) +++ head/sys/modules/cc/Makefile Tue Feb 1 07:05:14 2011 (r218155) @@ -1,6 +1,7 @@ # $FreeBSD$ -SUBDIR= cc_cubic \ +SUBDIR= cc_chd \ + cc_cubic \ cc_hd \ cc_htcp \ cc_vegas Added: head/sys/modules/cc/cc_chd/Makefile ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/sys/modules/cc/cc_chd/Makefile Tue Feb 1 07:05:14 2011 (r218155) @@ -0,0 +1,9 @@ +# $FreeBSD$ + +.include <bsd.own.mk> + +.PATH: ${.CURDIR}/../../../netinet/cc +KMOD= cc_chd +SRCS= cc_chd.c + +.include <bsd.kmod.mk> Added: head/sys/netinet/cc/cc_chd.c ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ head/sys/netinet/cc/cc_chd.c Tue Feb 1 07:05:14 2011 (r218155) @@ -0,0 +1,497 @@ +/*- + * Copyright (c) 2009-2010 + * Swinburne University of Technology, Melbourne, Australia + * Copyright (c) 2010-2011 The FreeBSD Foundation + * All rights reserved. + * + * This software was developed at the Centre for Advanced Internet + * Architectures, Swinburne University, by David Hayes and Lawrence Stewart, + * made possible in part by a grant from the Cisco University Research Program + * Fund at Community Foundation Silicon Valley. + * + * Portions of this software were developed at the Centre for Advanced Internet + * Architectures, Swinburne University of Technology, Melbourne, Australia by + * David Hayes under sponsorship from the FreeBSD Foundation. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +/* + * An implementation of the CAIA-Hamilton delay based congestion control + * algorithm, based on "Improved coexistence and loss tolerance for delay based + * TCP congestion control" by D. A. Hayes and G. Armitage., in 35th Annual IEEE + * Conference on Local Computer Networks (LCN 2010), Denver, Colorado, USA, + * 11-14 October 2010. + * + * Originally released as part of the NewTCP research project at Swinburne + * University's Centre for Advanced Internet Architectures, Melbourne, + * Australia, which was made possible in part by a grant from the Cisco + * University Research Program Fund at Community Foundation Silicon Valley. More + * details are available at: + * http://caia.swin.edu.au/urp/newtcp/ + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <sys/param.h> +#include <sys/kernel.h> +#include <sys/khelp.h> +#include <sys/limits.h> +#include <sys/malloc.h> +#include <sys/module.h> +#include <sys/queue.h> +#include <sys/socket.h> +#include <sys/socketvar.h> +#include <sys/sysctl.h> +#include <sys/systm.h> + +#include <net/if.h> +#include <net/vnet.h> + +#include <netinet/cc.h> +#include <netinet/tcp_seq.h> +#include <netinet/tcp_timer.h> +#include <netinet/tcp_var.h> + +#include <netinet/cc/cc_module.h> + +#include <netinet/khelp/h_ertt.h> + +#define CAST_PTR_INT(X) (*((int*)(X))) + +/* + * Private signal type for rate based congestion signal. + * See <netinet/cc.h> for appropriate bit-range to use for private signals. + */ +#define CC_CHD_DELAY 0x02000000 + +/* Largest possible number returned by random(). */ +#define RANDOM_MAX INT_MAX + +static void chd_ack_received(struct cc_var *ccv, uint16_t ack_type); +static void chd_cb_destroy(struct cc_var *ccv); +static int chd_cb_init(struct cc_var *ccv); +static void chd_cong_signal(struct cc_var *ccv, uint32_t signal_type); +static void chd_conn_init(struct cc_var *ccv); +static int chd_mod_init(void); + +struct chd { + /* + * Shadow window - keeps track of what the NewReno congestion window + * would have been if delay-based cwnd backoffs had not been made. This + * functionality aids coexistence with loss-based TCP flows which may be + * sharing links along the path. + */ + unsigned long shadow_w; + /* + * Loss-based TCP compatibility flag - When set, it turns on the shadow + * window functionality. + */ + int loss_compete; + /* The maximum round trip time seen within a measured rtt period. */ + int maxrtt_in_rtt; + /* The previous qdly that caused cwnd to backoff. */ + int prev_backoff_qdly; +}; + +static int ertt_id; + +static VNET_DEFINE(uint32_t, chd_qmin) = 5; +static VNET_DEFINE(uint32_t, chd_pmax) = 50; +static VNET_DEFINE(uint32_t, chd_loss_fair) = 1; +static VNET_DEFINE(uint32_t, chd_use_max) = 1; +static VNET_DEFINE(uint32_t, chd_qthresh) = 20; +#define V_chd_qthresh VNET(chd_qthresh) +#define V_chd_qmin VNET(chd_qmin) +#define V_chd_pmax VNET(chd_pmax) +#define V_chd_loss_fair VNET(chd_loss_fair) +#define V_chd_use_max VNET(chd_use_max) + +MALLOC_DECLARE(M_CHD); +MALLOC_DEFINE(M_CHD, "chd data", + "Per connection data required for the CHD congestion control algorithm"); + +struct cc_algo chd_cc_algo = { + .name = "chd", + .ack_received = chd_ack_received, + .cb_destroy = chd_cb_destroy, + .cb_init = chd_cb_init, + .cong_signal = chd_cong_signal, + .conn_init = chd_conn_init, + .mod_init = chd_mod_init +}; + +static __inline void +chd_window_decrease(struct cc_var *ccv) +{ + unsigned long win; + + win = min(CCV(ccv, snd_wnd), CCV(ccv, snd_cwnd)) / CCV(ccv, t_maxseg); + win -= max((win / 2), 1); + CCV(ccv, snd_ssthresh) = max(win, 2) * CCV(ccv, t_maxseg); +} + +/* + * Probabilistic backoff function. Returns 1 if we should backoff or 0 + * otherwise. The calculation of p is similar to the calculation of p in cc_hd. + */ +static __inline int +should_backoff(int qdly, int maxqdly, struct chd *chd_data) +{ + unsigned long p, rand; + + rand = random(); + + if (qdly < V_chd_qthresh) { + chd_data->loss_compete = 0; + p = (((RANDOM_MAX / 100) * V_chd_pmax) / + (V_chd_qthresh - V_chd_qmin)) * + (qdly - V_chd_qmin); + } else { + if (qdly > V_chd_qthresh) { + p = (((RANDOM_MAX / 100) * V_chd_pmax) / + (maxqdly - V_chd_qthresh)) * + (maxqdly - qdly); + if (V_chd_loss_fair && rand < p) + chd_data->loss_compete = 1; + } else { + p = (RANDOM_MAX / 100) * V_chd_pmax; + chd_data->loss_compete = 0; + } + } + + return (rand < p); +} + +static __inline void +chd_window_increase(struct cc_var *ccv, int new_measurement) +{ + struct chd *chd_data; + int incr; + + chd_data = ccv->cc_data; + incr = 0; + + if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh)) { + /* Adapted from NewReno slow start. */ + if (V_tcp_do_rfc3465) { + /* In slow-start with ABC enabled. */ + if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max)) { + /* Not due to RTO. */ + incr = min(ccv->bytes_this_ack, + V_tcp_abc_l_var * CCV(ccv, t_maxseg)); + } else { + /* Due to RTO. */ + incr = min(ccv->bytes_this_ack, + CCV(ccv, t_maxseg)); + } + } else + incr = CCV(ccv, t_maxseg); + + } else { /* Congestion avoidance. */ + if (V_tcp_do_rfc3465) { + if (ccv->flags & CCF_ABC_SENTAWND) { + ccv->flags &= ~CCF_ABC_SENTAWND; + incr = CCV(ccv, t_maxseg); + } + } else if (new_measurement) + incr = CCV(ccv, t_maxseg); + } + + if (chd_data->shadow_w > 0) { + /* Track NewReno window. */ + chd_data->shadow_w = min(chd_data->shadow_w + incr, + TCP_MAXWIN << CCV(ccv, snd_scale)); + } + + CCV(ccv,snd_cwnd) = min(CCV(ccv, snd_cwnd) + incr, + TCP_MAXWIN << CCV(ccv, snd_scale)); +} + +/* + * All ACK signals are used for timing measurements to determine delay-based + * congestion. However, window increases are only performed when + * ack_type == CC_ACK. + */ +static void +chd_ack_received(struct cc_var *ccv, uint16_t ack_type) +{ + struct chd *chd_data; + struct ertt *e_t; + int backoff, new_measurement, qdly, rtt; + + e_t = khelp_get_osd(CCV(ccv, osd), ertt_id); + chd_data = ccv->cc_data; + new_measurement = e_t->flags & ERTT_NEW_MEASUREMENT; + backoff = qdly = 0; + + chd_data->maxrtt_in_rtt = imax(e_t->rtt, chd_data->maxrtt_in_rtt); + + if (new_measurement) { + /* + * There is a new per RTT measurement, so check to see if there + * is delay based congestion. + */ + rtt = V_chd_use_max ? chd_data->maxrtt_in_rtt : e_t->rtt; + chd_data->maxrtt_in_rtt = 0; + + if (rtt && e_t->minrtt && !IN_RECOVERY(CCV(ccv, t_flags))) { + qdly = rtt - e_t->minrtt; + if (qdly > V_chd_qmin) { + /* + * Probabilistic delay based congestion + * indication. + */ + backoff = should_backoff(qdly, + e_t->maxrtt - e_t->minrtt, chd_data); + } else + chd_data->loss_compete = 0; + } + /* Reset per RTT measurement flag to start a new measurement. */ + e_t->flags &= ~ERTT_NEW_MEASUREMENT; + } + + if (backoff) { + /* + * Update shadow_w before delay based backoff. + */ + if (chd_data->loss_compete || + qdly > chd_data->prev_backoff_qdly) { + /* + * Delay is higher than when we backed off previously, + * so it is possible that this flow is competing with + * loss based flows. + */ + chd_data->shadow_w = max(CCV(ccv, snd_cwnd), + chd_data->shadow_w); + } else { + /* + * Reset shadow_w, as it is probable that this flow is + * not competing with loss based flows at the moment. + */ + chd_data->shadow_w = 0; + } + + chd_data->prev_backoff_qdly = qdly; + /* + * Send delay-based congestion signal to the congestion signal + * handler. + */ + chd_cong_signal(ccv, CC_CHD_DELAY); + + } else if (ack_type == CC_ACK) + chd_window_increase(ccv, new_measurement); +} + +static void +chd_cb_destroy(struct cc_var *ccv) +{ + + if (ccv->cc_data != NULL) + free(ccv->cc_data, M_CHD); +} + +static int +chd_cb_init(struct cc_var *ccv) +{ + struct chd *chd_data; + + chd_data = malloc(sizeof(struct chd), M_CHD, M_NOWAIT); + if (chd_data == NULL) + return (ENOMEM); + + chd_data->shadow_w = 0; + ccv->cc_data = chd_data; + + return (0); +} + +static void +chd_cong_signal(struct cc_var *ccv, uint32_t signal_type) +{ + struct ertt *e_t; + struct chd *chd_data; + int qdly; + + e_t = khelp_get_osd(CCV(ccv, osd), ertt_id); + chd_data = ccv->cc_data; + qdly = imax(e_t->rtt, chd_data->maxrtt_in_rtt) - e_t->minrtt; + + switch(signal_type) { + case CC_CHD_DELAY: + chd_window_decrease(ccv); /* Set new ssthresh. */ + CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh); + CCV(ccv, snd_recover) = CCV(ccv, snd_max); + ENTER_CONGRECOVERY(CCV(ccv, t_flags)); + break; + + case CC_NDUPACK: /* Packet loss. */ + /* + * Only react to loss as a congestion signal if qdly > + * V_chd_qthresh. If qdly is less than qthresh, presume that + * this is a non congestion related loss. If qdly is greater + * than qthresh, assume that we are competing with loss based + * tcp flows and restore window from any unnecessary backoffs, + * before the decrease. + */ + if (!IN_RECOVERY(CCV(ccv, t_flags)) && qdly > V_chd_qthresh) { + if (chd_data->loss_compete) { + CCV(ccv, snd_cwnd) = max(CCV(ccv, snd_cwnd), + chd_data->shadow_w); + } + chd_window_decrease(ccv); + } else { + /* + * This loss isn't congestion related, or already + * recovering from congestion. + */ + CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd); + CCV(ccv, snd_recover) = CCV(ccv, snd_max); + } + + if (chd_data->shadow_w > 0) { + chd_data->shadow_w = max(chd_data->shadow_w / + CCV(ccv, t_maxseg) / 2, 2) * CCV(ccv, t_maxseg); + } + ENTER_FASTRECOVERY(CCV(ccv, t_flags)); + break; + + default: + newreno_cc_algo.cong_signal(ccv, signal_type); + } +} + +static void +chd_conn_init(struct cc_var *ccv) +{ + struct chd *chd_data; + + chd_data = ccv->cc_data; + chd_data->prev_backoff_qdly = 0; + chd_data->maxrtt_in_rtt = 0; + chd_data->loss_compete = 0; + /* + * Initialise the shadow_cwnd to be equal to snd_cwnd in case we are + * competing with loss based flows from the start. + */ + chd_data->shadow_w = CCV(ccv, snd_cwnd); +} + +static int +chd_mod_init(void) +{ + + ertt_id = khelp_get_id("ertt"); + if (ertt_id <= 0) { + printf("%s: h_ertt module not found\n", __func__); + return (ENOENT); + } + + chd_cc_algo.after_idle = newreno_cc_algo.after_idle; + chd_cc_algo.post_recovery = newreno_cc_algo.post_recovery; + + return (0); +} + +static int +chd_loss_fair_handler(SYSCTL_HANDLER_ARGS) +{ + int error; + uint32_t new; + + new = V_chd_loss_fair; + error = sysctl_handle_int(oidp, &new, 0, req); + if (error == 0 && req->newptr != NULL) { + if (CAST_PTR_INT(req->newptr) > 1) + error = EINVAL; + else + V_chd_loss_fair = new; + } + + return (error); +} + +static int +chd_pmax_handler(SYSCTL_HANDLER_ARGS) +{ + int error; + uint32_t new; + + new = V_chd_pmax; + error = sysctl_handle_int(oidp, &new, 0, req); + if (error == 0 && req->newptr != NULL) { + if (CAST_PTR_INT(req->newptr) == 0 || + CAST_PTR_INT(req->newptr) > 100) + error = EINVAL; + else + V_chd_pmax = new; + } + + return (error); +} + +static int +chd_qthresh_handler(SYSCTL_HANDLER_ARGS) +{ + int error; + uint32_t new; + + new = V_chd_qthresh; + error = sysctl_handle_int(oidp, &new, 0, req); + if (error == 0 && req->newptr != NULL) { + if (CAST_PTR_INT(req->newptr) <= V_chd_qmin) + error = EINVAL; + else + V_chd_qthresh = new; + } + + return (error); +} + +SYSCTL_DECL(_net_inet_tcp_cc_chd); +SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, chd, CTLFLAG_RW, NULL, + "CAIA Hamilton delay-based congestion control related settings"); + +SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, loss_fair, + CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_loss_fair), 1, &chd_loss_fair_handler, + "IU", "Flag to enable shadow window functionality."); + +SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, pmax, + CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_pmax), 5, &chd_pmax_handler, + "IU", "Per RTT maximum backoff probability as a percentage"); + +SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, queue_threshold, + CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_qthresh), 20, &chd_qthresh_handler, + "IU", "Queueing congestion threshold in ticks"); + +SYSCTL_VNET_UINT(_net_inet_tcp_cc_chd, OID_AUTO, queue_min, + CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_qmin), 5, + "Minimum queueing delay threshold in ticks"); + +SYSCTL_VNET_UINT(_net_inet_tcp_cc_chd, OID_AUTO, use_max, + CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_use_max), 1, + "Use the maximum RTT seen within the measurement period (RTT) " + "as the basic delay measurement for the algorithm."); + +DECLARE_CC_MODULE(chd, &chd_cc_algo); +MODULE_DEPEND(chd, ertt, 1, 1, 1);
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201102010705.p1175EgG061905>