Date: Sat, 28 May 2011 05:28:00 +0000 (UTC) From: Lawrence Stewart <lstewart@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org Subject: svn commit: r222404 - in stable/8/sys: modules/cc modules/cc/cc_htcp netinet/cc Message-ID: <201105280528.p4S5S0a8069661@svn.freebsd.org>
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Author: lstewart Date: Sat May 28 05:28:00 2011 New Revision: 222404 URL: http://svn.freebsd.org/changeset/base/222404 Log: MFC r216115: Import a clean-room implementation of the experimental H-TCP congestion control algorithm based on the Internet-Draft "draft-leith-tcp-htcp-06.txt". It is implemented as a kernel module compatible with the recently committed modular congestion control framework. H-TCP was designed to provide increased throughput in fast and long-distance networks. It attempts to maintain fairness when competing with legacy NewReno TCP in lower speed scenarios where NewReno is able to operate adequately. The paper "H-TCP: A framework for congestion control in high-speed and long-distance networks" provides additional detail. In collaboration with: David Hayes <dahayes at swin edu au> and Grenville Armitage <garmitage at swin edu au> Sponsored by: FreeBSD Foundation Reviewed by: rpaulo Added: stable/8/sys/modules/cc/cc_htcp/ - copied from r216115, head/sys/modules/cc/cc_htcp/ stable/8/sys/netinet/cc/cc_htcp.c - copied unchanged from r216115, head/sys/netinet/cc/cc_htcp.c Modified: stable/8/sys/modules/cc/Makefile Directory Properties: stable/8/sys/ (props changed) stable/8/sys/amd64/include/xen/ (props changed) stable/8/sys/cddl/contrib/opensolaris/ (props changed) stable/8/sys/contrib/dev/acpica/ (props changed) stable/8/sys/contrib/pf/ (props changed) Modified: stable/8/sys/modules/cc/Makefile ============================================================================== --- stable/8/sys/modules/cc/Makefile Sat May 28 05:17:52 2011 (r222403) +++ stable/8/sys/modules/cc/Makefile Sat May 28 05:28:00 2011 (r222404) @@ -1,5 +1,6 @@ # $FreeBSD$ -SUBDIR= cc_cubic +SUBDIR= cc_cubic \ + cc_htcp .include <bsd.subdir.mk> Copied: stable/8/sys/netinet/cc/cc_htcp.c (from r216115, head/sys/netinet/cc/cc_htcp.c) ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ stable/8/sys/netinet/cc/cc_htcp.c Sat May 28 05:28:00 2011 (r222404, copy of r216115, head/sys/netinet/cc/cc_htcp.c) @@ -0,0 +1,521 @@ +/*- + * Copyright (c) 2007-2008 + * Swinburne University of Technology, Melbourne, Australia + * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> + * Copyright (c) 2010 The FreeBSD Foundation + * All rights reserved. + * + * This software was developed at the Centre for Advanced Internet + * Architectures, Swinburne University, by Lawrence Stewart and James Healy, + * 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 H-TCP congestion control algorithm for FreeBSD, + * based on the Internet Draft "draft-leith-tcp-htcp-06.txt" by Leith and + * Shorten. 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/limits.h> +#include <sys/malloc.h> +#include <sys/module.h> +#include <sys/socket.h> +#include <sys/socketvar.h> +#include <sys/sysctl.h> +#include <sys/systm.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> + +/* Fixed point math shifts. */ +#define HTCP_SHIFT 8 +#define HTCP_ALPHA_INC_SHIFT 4 + +#define HTCP_INIT_ALPHA 1 +#define HTCP_DELTA_L hz /* 1 sec in ticks. */ +#define HTCP_MINBETA 128 /* 0.5 << HTCP_SHIFT. */ +#define HTCP_MAXBETA 204 /* ~0.8 << HTCP_SHIFT. */ +#define HTCP_MINROWE 26 /* ~0.1 << HTCP_SHIFT. */ +#define HTCP_MAXROWE 512 /* 2 << HTCP_SHIFT. */ + +/* RTT_ref (ms) used in the calculation of alpha if RTT scaling is enabled. */ +#define HTCP_RTT_REF 100 + +/* Don't trust SRTT until this many samples have been taken. */ +#define HTCP_MIN_RTT_SAMPLES 8 + +/* + * HTCP_CALC_ALPHA performs a fixed point math calculation to determine the + * value of alpha, based on the function defined in the HTCP spec. + * + * i.e. 1 + 10(delta - delta_l) + ((delta - delta_l) / 2) ^ 2 + * + * "diff" is passed in to the macro as "delta - delta_l" and is expected to be + * in units of ticks. + * + * The joyousnous of fixed point maths means our function implementation looks a + * little funky... + * + * In order to maintain some precision in the calculations, a fixed point shift + * HTCP_ALPHA_INC_SHIFT is used to ensure the integer divisions don't + * truncate the results too badly. + * + * The "16" value is the "1" term in the alpha function shifted up by + * HTCP_ALPHA_INC_SHIFT + * + * The "160" value is the "10" multiplier in the alpha function multiplied by + * 2^HTCP_ALPHA_INC_SHIFT + * + * Specifying these as constants reduces the computations required. After + * up-shifting all the terms in the function and performing the required + * calculations, we down-shift the final result by HTCP_ALPHA_INC_SHIFT to + * ensure it is back in the correct range. + * + * The "hz" terms are required as kernels can be configured to run with + * different tick timers, which we have to adjust for in the alpha calculation + * (which originally was defined in terms of seconds). + * + * We also have to be careful to constrain the value of diff such that it won't + * overflow whilst performing the calculation. The middle term i.e. (160 * diff) + * / hz is the limiting factor in the calculation. We must constrain diff to be + * less than the max size of an int divided by the constant 160 figure + * i.e. diff < INT_MAX / 160 + * + * NB: Changing HTCP_ALPHA_INC_SHIFT will require you to MANUALLY update the + * constants used in this function! + */ +#define HTCP_CALC_ALPHA(diff) \ +((\ + (16) + \ + ((160 * (diff)) / hz) + \ + (((diff) / hz) * (((diff) << HTCP_ALPHA_INC_SHIFT) / (4 * hz))) \ +) >> HTCP_ALPHA_INC_SHIFT) + +static void htcp_ack_received(struct cc_var *ccv, uint16_t type); +static void htcp_cb_destroy(struct cc_var *ccv); +static int htcp_cb_init(struct cc_var *ccv); +static void htcp_cong_signal(struct cc_var *ccv, uint32_t type); +static int htcp_mod_init(void); +static void htcp_post_recovery(struct cc_var *ccv); +static void htcp_recalc_alpha(struct cc_var *ccv); +static void htcp_recalc_beta(struct cc_var *ccv); +static void htcp_record_rtt(struct cc_var *ccv); +static void htcp_ssthresh_update(struct cc_var *ccv); + +struct htcp { + /* cwnd before entering cong recovery. */ + unsigned long prev_cwnd; + /* cwnd additive increase parameter. */ + int alpha; + /* cwnd multiplicative decrease parameter. */ + int beta; + /* Largest rtt seen for the flow. */ + int maxrtt; + /* Shortest rtt seen for the flow. */ + int minrtt; + /* Time of last congestion event in ticks. */ + int t_last_cong; +}; + +static int htcp_rtt_ref; +/* + * The maximum number of ticks the value of diff can reach in + * htcp_recalc_alpha() before alpha will stop increasing due to overflow. + * See comment above HTCP_CALC_ALPHA for more info. + */ +static int htcp_max_diff = INT_MAX / ((1 << HTCP_ALPHA_INC_SHIFT) * 10); + +/* Per-netstack vars. */ +static VNET_DEFINE(uint8_t, htcp_adaptive_backoff) = 0; +static VNET_DEFINE(uint8_t, htcp_rtt_scaling) = 0; +#define V_htcp_adaptive_backoff VNET(htcp_adaptive_backoff) +#define V_htcp_rtt_scaling VNET(htcp_rtt_scaling) + +MALLOC_DECLARE(M_HTCP); +MALLOC_DEFINE(M_HTCP, "htcp data", + "Per connection data required for the HTCP congestion control algorithm"); + +struct cc_algo htcp_cc_algo = { + .name = "htcp", + .ack_received = htcp_ack_received, + .cb_destroy = htcp_cb_destroy, + .cb_init = htcp_cb_init, + .cong_signal = htcp_cong_signal, + .mod_init = htcp_mod_init, + .post_recovery = htcp_post_recovery, +}; + +static void +htcp_ack_received(struct cc_var *ccv, uint16_t type) +{ + struct htcp *htcp_data; + + htcp_data = ccv->cc_data; + htcp_record_rtt(ccv); + + /* + * Regular ACK and we're not in cong/fast recovery and we're cwnd + * limited and we're either not doing ABC or are slow starting or are + * doing ABC and we've sent a cwnd's worth of bytes. + */ + if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) && + (ccv->flags & CCF_CWND_LIMITED) && (!V_tcp_do_rfc3465 || + CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) || + (V_tcp_do_rfc3465 && ccv->flags & CCF_ABC_SENTAWND))) { + htcp_recalc_beta(ccv); + htcp_recalc_alpha(ccv); + /* + * Use the logic in NewReno ack_received() for slow start and + * for the first HTCP_DELTA_L ticks after either the flow starts + * or a congestion event (when alpha equals 1). + */ + if (htcp_data->alpha == 1 || + CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh)) + newreno_cc_algo.ack_received(ccv, type); + else { + if (V_tcp_do_rfc3465) { + /* Increment cwnd by alpha segments. */ + CCV(ccv, snd_cwnd) += htcp_data->alpha * + CCV(ccv, t_maxseg); + ccv->flags &= ~CCF_ABC_SENTAWND; + } else + /* + * Increment cwnd by alpha/cwnd segments to + * approximate an increase of alpha segments + * per RTT. + */ + CCV(ccv, snd_cwnd) += (((htcp_data->alpha << + HTCP_SHIFT) / (CCV(ccv, snd_cwnd) / + CCV(ccv, t_maxseg))) * CCV(ccv, t_maxseg)) + >> HTCP_SHIFT; + } + } +} + +static void +htcp_cb_destroy(struct cc_var *ccv) +{ + + if (ccv->cc_data != NULL) + free(ccv->cc_data, M_HTCP); +} + +static int +htcp_cb_init(struct cc_var *ccv) +{ + struct htcp *htcp_data; + + htcp_data = malloc(sizeof(struct htcp), M_HTCP, M_NOWAIT); + + if (htcp_data == NULL) + return (ENOMEM); + + /* Init some key variables with sensible defaults. */ + htcp_data->alpha = HTCP_INIT_ALPHA; + htcp_data->beta = HTCP_MINBETA; + htcp_data->maxrtt = TCPTV_SRTTBASE; + htcp_data->minrtt = TCPTV_SRTTBASE; + htcp_data->prev_cwnd = 0; + htcp_data->t_last_cong = ticks; + + ccv->cc_data = htcp_data; + + return (0); +} + +/* + * Perform any necessary tasks before we enter congestion recovery. + */ +static void +htcp_cong_signal(struct cc_var *ccv, uint32_t type) +{ + struct htcp *htcp_data; + + htcp_data = ccv->cc_data; + + switch (type) { + case CC_NDUPACK: + if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) { + if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { + /* + * Apply hysteresis to maxrtt to ensure + * reductions in the RTT are reflected in our + * measurements. + */ + htcp_data->maxrtt = (htcp_data->minrtt + + (htcp_data->maxrtt - htcp_data->minrtt) * + 95) / 100; + htcp_ssthresh_update(ccv); + htcp_data->t_last_cong = ticks; + htcp_data->prev_cwnd = CCV(ccv, snd_cwnd); + } + ENTER_RECOVERY(CCV(ccv, t_flags)); + } + break; + + case CC_ECN: + if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { + /* + * Apply hysteresis to maxrtt to ensure reductions in + * the RTT are reflected in our measurements. + */ + htcp_data->maxrtt = (htcp_data->minrtt + (htcp_data->maxrtt - + htcp_data->minrtt) * 95) / 100; + htcp_ssthresh_update(ccv); + CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh); + htcp_data->t_last_cong = ticks; + htcp_data->prev_cwnd = CCV(ccv, snd_cwnd); + ENTER_CONGRECOVERY(CCV(ccv, t_flags)); + } + break; + + case CC_RTO: + /* + * Grab the current time and record it so we know when the + * most recent congestion event was. Only record it when the + * timeout has fired more than once, as there is a reasonable + * chance the first one is a false alarm and may not indicate + * congestion. + */ + if (CCV(ccv, t_rxtshift) >= 2) + htcp_data->t_last_cong = ticks; + break; + } +} + +static int +htcp_mod_init(void) +{ + + htcp_cc_algo.after_idle = newreno_cc_algo.after_idle; + + /* + * HTCP_RTT_REF is defined in ms, and t_srtt in the tcpcb is stored in + * units of TCP_RTT_SCALE*hz. Scale HTCP_RTT_REF to be in the same units + * as t_srtt. + */ + htcp_rtt_ref = (HTCP_RTT_REF * TCP_RTT_SCALE * hz) / 1000; + + return (0); +} + +/* + * Perform any necessary tasks before we exit congestion recovery. + */ +static void +htcp_post_recovery(struct cc_var *ccv) +{ + struct htcp *htcp_data; + + htcp_data = ccv->cc_data; + + if (IN_FASTRECOVERY(CCV(ccv, t_flags))) { + /* + * If inflight data is less than ssthresh, set cwnd + * conservatively to avoid a burst of data, as suggested in the + * NewReno RFC. Otherwise, use the HTCP method. + * + * XXXLAS: Find a way to do this without needing curack + */ + if (SEQ_GT(ccv->curack + CCV(ccv, snd_ssthresh), + CCV(ccv, snd_max))) + CCV(ccv, snd_cwnd) = CCV(ccv, snd_max) - ccv->curack + + CCV(ccv, t_maxseg); + else + CCV(ccv, snd_cwnd) = max(1, ((htcp_data->beta * + htcp_data->prev_cwnd / CCV(ccv, t_maxseg)) + >> HTCP_SHIFT)) * CCV(ccv, t_maxseg); + } +} + +static void +htcp_recalc_alpha(struct cc_var *ccv) +{ + struct htcp *htcp_data; + int alpha, diff, now; + + htcp_data = ccv->cc_data; + now = ticks; + + /* + * If ticks has wrapped around (will happen approximately once every 49 + * days on a machine with the default kern.hz=1000) and a flow straddles + * the wrap point, our alpha calcs will be completely wrong. We cut our + * losses and restart alpha from scratch by setting t_last_cong = now - + * HTCP_DELTA_L. + * + * This does not deflate our cwnd at all. It simply slows the rate cwnd + * is growing by until alpha regains the value it held prior to taking + * this drastic measure. + */ + if (now < htcp_data->t_last_cong) + htcp_data->t_last_cong = now - HTCP_DELTA_L; + + diff = now - htcp_data->t_last_cong - HTCP_DELTA_L; + + /* Cap alpha if the value of diff would overflow HTCP_CALC_ALPHA(). */ + if (diff < htcp_max_diff) { + /* + * If it has been more than HTCP_DELTA_L ticks since congestion, + * increase alpha according to the function defined in the spec. + */ + if (diff > 0) { + alpha = HTCP_CALC_ALPHA(diff); + + /* + * Adaptive backoff fairness adjustment: + * 2 * (1 - beta) * alpha_raw + */ + if (V_htcp_adaptive_backoff) + alpha = max(1, (2 * ((1 << HTCP_SHIFT) - + htcp_data->beta) * alpha) >> HTCP_SHIFT); + + /* + * RTT scaling: (RTT / RTT_ref) * alpha + * alpha will be the raw value from HTCP_CALC_ALPHA() if + * adaptive backoff is off, or the adjusted value if + * adaptive backoff is on. + */ + if (V_htcp_rtt_scaling) + alpha = max(1, (min(max(HTCP_MINROWE, + (CCV(ccv, t_srtt) << HTCP_SHIFT) / + htcp_rtt_ref), HTCP_MAXROWE) * alpha) + >> HTCP_SHIFT); + + } else + alpha = 1; + + htcp_data->alpha = alpha; + } +} + +static void +htcp_recalc_beta(struct cc_var *ccv) +{ + struct htcp *htcp_data; + + htcp_data = ccv->cc_data; + + /* + * TCPTV_SRTTBASE is the initialised value of each connection's SRTT, so + * we only calc beta if the connection's SRTT has been changed from its + * inital value. beta is bounded to ensure it is always between + * HTCP_MINBETA and HTCP_MAXBETA. + */ + if (V_htcp_adaptive_backoff && htcp_data->minrtt != TCPTV_SRTTBASE && + htcp_data->maxrtt != TCPTV_SRTTBASE) + htcp_data->beta = min(max(HTCP_MINBETA, + (htcp_data->minrtt << HTCP_SHIFT) / htcp_data->maxrtt), + HTCP_MAXBETA); + else + htcp_data->beta = HTCP_MINBETA; +} + +/* + * Record the minimum and maximum RTT seen for the connection. These are used in + * the calculation of beta if adaptive backoff is enabled. + */ +static void +htcp_record_rtt(struct cc_var *ccv) +{ + struct htcp *htcp_data; + + htcp_data = ccv->cc_data; + + /* XXXLAS: Should there be some hysteresis for minrtt? */ + + /* + * Record the current SRTT as our minrtt if it's the smallest we've seen + * or minrtt is currently equal to its initialised value. Ignore SRTT + * until a min number of samples have been taken. + */ + if ((CCV(ccv, t_srtt) < htcp_data->minrtt || + htcp_data->minrtt == TCPTV_SRTTBASE) && + (CCV(ccv, t_rttupdated) >= HTCP_MIN_RTT_SAMPLES)) + htcp_data->minrtt = CCV(ccv, t_srtt); + + /* + * Record the current SRTT as our maxrtt if it's the largest we've + * seen. Ignore SRTT until a min number of samples have been taken. + */ + if (CCV(ccv, t_srtt) > htcp_data->maxrtt + && CCV(ccv, t_rttupdated) >= HTCP_MIN_RTT_SAMPLES) + htcp_data->maxrtt = CCV(ccv, t_srtt); +} + +/* + * Update the ssthresh in the event of congestion. + */ +static void +htcp_ssthresh_update(struct cc_var *ccv) +{ + struct htcp *htcp_data; + + htcp_data = ccv->cc_data; + + /* + * On the first congestion event, set ssthresh to cwnd * 0.5, on + * subsequent congestion events, set it to cwnd * beta. + */ + if (CCV(ccv, snd_ssthresh) == TCP_MAXWIN << TCP_MAX_WINSHIFT) + CCV(ccv, snd_ssthresh) = (CCV(ccv, snd_cwnd) * HTCP_MINBETA) + >> HTCP_SHIFT; + else { + htcp_recalc_beta(ccv); + CCV(ccv, snd_ssthresh) = (CCV(ccv, snd_cwnd) * htcp_data->beta) + >> HTCP_SHIFT; + } +} + + +SYSCTL_DECL(_net_inet_tcp_cc_htcp); +SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, htcp, CTLFLAG_RW, + NULL, "H-TCP related settings"); +SYSCTL_VNET_UINT(_net_inet_tcp_cc_htcp, OID_AUTO, adaptive_backoff, CTLFLAG_RW, + &VNET_NAME(htcp_adaptive_backoff), 0, "enable H-TCP adaptive backoff"); +SYSCTL_VNET_UINT(_net_inet_tcp_cc_htcp, OID_AUTO, rtt_scaling, CTLFLAG_RW, + &VNET_NAME(htcp_rtt_scaling), 0, "enable H-TCP RTT scaling"); + +DECLARE_CC_MODULE(htcp, &htcp_cc_algo);
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