cc_vegas.c

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    1 /*-
    2  * Copyright (c) 2009-2010
    3  *      Swinburne University of Technology, Melbourne, Australia
    4  * Copyright (c) 2010 Lawrence Stewart <lstewart@freebsd.org>
    5  * Copyright (c) 2010-2011 The FreeBSD Foundation
    6  * All rights reserved.
    7  *
    8  * This software was developed at the Centre for Advanced Internet
    9  * Architectures, Swinburne University of Technology, by David Hayes and
   10  * Lawrence Stewart, made possible in part by a grant from the Cisco University
   11  * Research Program Fund at Community Foundation Silicon Valley.
   12  *
   13  * Portions of this software were developed at the Centre for Advanced Internet
   14  * Architectures, Swinburne University of Technology, Melbourne, Australia by
   15  * David Hayes under sponsorship from the FreeBSD Foundation.
   16  *
   17  * Redistribution and use in source and binary forms, with or without
   18  * modification, are permitted provided that the following conditions
   19  * are met:
   20  * 1. Redistributions of source code must retain the above copyright
   21  *    notice, this list of conditions and the following disclaimer.
   22  * 2. Redistributions in binary form must reproduce the above copyright
   23  *    notice, this list of conditions and the following disclaimer in the
   24  *    documentation and/or other materials provided with the distribution.
   25  *
   26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   29  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   36  * SUCH DAMAGE.
   37  */
   38 
   39 /*
   40  * An implementation of the Vegas congestion control algorithm for FreeBSD,
   41  * based on L. S. Brakmo and L. L. Peterson, "TCP Vegas: end to end congestion
   42  * avoidance on a global internet", IEEE J. Sel. Areas Commun., vol. 13, no. 8,
   43  * pp. 1465-1480, Oct. 1995. The original Vegas duplicate ack policy has not
   44  * been implemented, since clock ticks are not as coarse as they were (i.e.
   45  * 500ms) when Vegas was designed. Also, packets are timed once per RTT as in
   46  * the original paper.
   47  *
   48  * Originally released as part of the NewTCP research project at Swinburne
   49  * University of Technology's Centre for Advanced Internet Architectures,
   50  * Melbourne, Australia, which was made possible in part by a grant from the
   51  * Cisco University Research Program Fund at Community Foundation Silicon
   52  * Valley. More details are available at:
   53  *   http://caia.swin.edu.au/urp/newtcp/
   54  */
   55 
   56 #include <sys/cdefs.h>
   57 __FBSDID("$FreeBSD: releng/10.3/sys/netinet/cc/cc_vegas.c 220592 2011-04-13 11:28:46Z pluknet $");
   58 
   59 #include <sys/param.h>
   60 #include <sys/kernel.h>
   61 #include <sys/khelp.h>
   62 #include <sys/malloc.h>
   63 #include <sys/module.h>
   64 #include <sys/queue.h>
   65 #include <sys/socket.h>
   66 #include <sys/socketvar.h>
   67 #include <sys/sysctl.h>
   68 #include <sys/systm.h>
   69 
   70 #include <net/if.h>
   71 #include <net/vnet.h>
   72 
   73 #include <netinet/cc.h>
   74 #include <netinet/tcp_seq.h>
   75 #include <netinet/tcp_timer.h>
   76 #include <netinet/tcp_var.h>
   77 
   78 #include <netinet/cc/cc_module.h>
   79 
   80 #include <netinet/khelp/h_ertt.h>
   81 
   82 #define CAST_PTR_INT(X) (*((int*)(X)))
   83 
   84 /*
   85  * Private signal type for rate based congestion signal.
   86  * See <netinet/cc.h> for appropriate bit-range to use for private signals.
   87  */
   88 #define CC_VEGAS_RATE   0x01000000
   89 
   90 static void     vegas_ack_received(struct cc_var *ccv, uint16_t ack_type);
   91 static void     vegas_cb_destroy(struct cc_var *ccv);
   92 static int      vegas_cb_init(struct cc_var *ccv);
   93 static void     vegas_cong_signal(struct cc_var *ccv, uint32_t signal_type);
   94 static void     vegas_conn_init(struct cc_var *ccv);
   95 static int      vegas_mod_init(void);
   96 
   97 struct vegas {
   98         int slow_start_toggle;
   99 };
  100 
  101 static int32_t ertt_id;
  102 
  103 static VNET_DEFINE(uint32_t, vegas_alpha) = 1;
  104 static VNET_DEFINE(uint32_t, vegas_beta) = 3;
  105 #define V_vegas_alpha   VNET(vegas_alpha)
  106 #define V_vegas_beta    VNET(vegas_beta)
  107 
  108 static MALLOC_DEFINE(M_VEGAS, "vegas data",
  109     "Per connection data required for the Vegas congestion control algorithm");
  110 
  111 struct cc_algo vegas_cc_algo = {
  112         .name = "vegas",
  113         .ack_received = vegas_ack_received,
  114         .cb_destroy = vegas_cb_destroy,
  115         .cb_init = vegas_cb_init,
  116         .cong_signal = vegas_cong_signal,
  117         .conn_init = vegas_conn_init,
  118         .mod_init = vegas_mod_init
  119 };
  120 
  121 /*
  122  * The vegas window adjustment is done once every RTT, as indicated by the
  123  * ERTT_NEW_MEASUREMENT flag. This flag is reset once the new measurment data
  124  * has been used.
  125  */
  126 static void
  127 vegas_ack_received(struct cc_var *ccv, uint16_t ack_type)
  128 {
  129         struct ertt *e_t;
  130         struct vegas *vegas_data;
  131         long actual_tx_rate, expected_tx_rate, ndiff;
  132 
  133         e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
  134         vegas_data = ccv->cc_data;
  135 
  136         if (e_t->flags & ERTT_NEW_MEASUREMENT) { /* Once per RTT. */
  137                 if (e_t->minrtt && e_t->markedpkt_rtt) {
  138                         expected_tx_rate = e_t->marked_snd_cwnd / e_t->minrtt;
  139                         actual_tx_rate = e_t->bytes_tx_in_marked_rtt /
  140                             e_t->markedpkt_rtt;
  141                         ndiff = (expected_tx_rate - actual_tx_rate) *
  142                             e_t->minrtt / CCV(ccv, t_maxseg);
  143 
  144                         if (ndiff < V_vegas_alpha) {
  145                                 if (CCV(ccv, snd_cwnd) <=
  146                                     CCV(ccv, snd_ssthresh)) {
  147                                         vegas_data->slow_start_toggle =
  148                                             vegas_data->slow_start_toggle ?
  149                                             0 : 1;
  150                                 } else {
  151                                         vegas_data->slow_start_toggle = 0;
  152                                         CCV(ccv, snd_cwnd) =
  153                                             min(CCV(ccv, snd_cwnd) +
  154                                             CCV(ccv, t_maxseg),
  155                                             TCP_MAXWIN << CCV(ccv, snd_scale));
  156                                 }
  157                         } else if (ndiff > V_vegas_beta) {
  158                                 /* Rate-based congestion. */
  159                                 vegas_cong_signal(ccv, CC_VEGAS_RATE);
  160                                 vegas_data->slow_start_toggle = 0;
  161                         }
  162                 }
  163                 e_t->flags &= ~ERTT_NEW_MEASUREMENT;
  164         }
  165 
  166         if (vegas_data->slow_start_toggle)
  167                 newreno_cc_algo.ack_received(ccv, ack_type);
  168 }
  169 
  170 static void
  171 vegas_cb_destroy(struct cc_var *ccv)
  172 {
  173 
  174         if (ccv->cc_data != NULL)
  175                 free(ccv->cc_data, M_VEGAS);
  176 }
  177 
  178 static int
  179 vegas_cb_init(struct cc_var *ccv)
  180 {
  181         struct vegas *vegas_data;
  182 
  183         vegas_data = malloc(sizeof(struct vegas), M_VEGAS, M_NOWAIT);
  184 
  185         if (vegas_data == NULL)
  186                 return (ENOMEM);
  187 
  188         vegas_data->slow_start_toggle = 1;
  189         ccv->cc_data = vegas_data;
  190 
  191         return (0);
  192 }
  193 
  194 /*
  195  * If congestion has been triggered triggered by the Vegas measured rates, it is
  196  * handled here, otherwise it falls back to newreno's congestion handling.
  197  */
  198 static void
  199 vegas_cong_signal(struct cc_var *ccv, uint32_t signal_type)
  200 {
  201         struct vegas *vegas_data;
  202         int presignalrecov;
  203 
  204         vegas_data = ccv->cc_data;
  205 
  206         if (IN_RECOVERY(CCV(ccv, t_flags)))
  207                 presignalrecov = 1;
  208         else
  209                 presignalrecov = 0;
  210 
  211         switch(signal_type) {
  212         case CC_VEGAS_RATE:
  213                 if (!IN_RECOVERY(CCV(ccv, t_flags))) {
  214                         CCV(ccv, snd_cwnd) = max(2 * CCV(ccv, t_maxseg),
  215                             CCV(ccv, snd_cwnd) - CCV(ccv, t_maxseg));
  216                         if (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh))
  217                                 /* Exit slow start. */
  218                                 CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
  219                 }
  220                 break;
  221 
  222         default:
  223                 newreno_cc_algo.cong_signal(ccv, signal_type);
  224         }
  225 
  226         if (IN_RECOVERY(CCV(ccv, t_flags)) && !presignalrecov)
  227                 vegas_data->slow_start_toggle =
  228                     (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh)) ? 1 : 0;
  229 }
  230 
  231 static void
  232 vegas_conn_init(struct cc_var *ccv)
  233 {
  234         struct vegas *vegas_data;
  235 
  236         vegas_data = ccv->cc_data;
  237         vegas_data->slow_start_toggle = 1;
  238 }
  239 
  240 static int
  241 vegas_mod_init(void)
  242 {
  243 
  244         ertt_id = khelp_get_id("ertt");
  245         if (ertt_id <= 0) {
  246                 printf("%s: h_ertt module not found\n", __func__);
  247                 return (ENOENT);
  248         }
  249 
  250         vegas_cc_algo.after_idle = newreno_cc_algo.after_idle;
  251         vegas_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
  252 
  253         return (0);
  254 }
  255 
  256 static int
  257 vegas_alpha_handler(SYSCTL_HANDLER_ARGS)
  258 {
  259         int error;
  260         uint32_t new;
  261 
  262         new = V_vegas_alpha;
  263         error = sysctl_handle_int(oidp, &new, 0, req);
  264         if (error == 0 && req->newptr != NULL) {
  265                 if (CAST_PTR_INT(req->newptr) < 1 ||
  266                     CAST_PTR_INT(req->newptr) > V_vegas_beta)
  267                         error = EINVAL;
  268                 else
  269                         V_vegas_alpha = new;
  270         }
  271 
  272         return (error);
  273 }
  274 
  275 static int
  276 vegas_beta_handler(SYSCTL_HANDLER_ARGS)
  277 {
  278         int error;
  279         uint32_t new;
  280 
  281         new = V_vegas_beta;
  282         error = sysctl_handle_int(oidp, &new, 0, req);
  283         if (error == 0 && req->newptr != NULL) {
  284                 if (CAST_PTR_INT(req->newptr) < 1 ||
  285                     CAST_PTR_INT(req->newptr) < V_vegas_alpha)
  286                          error = EINVAL;
  287                 else
  288                         V_vegas_beta = new;
  289         }
  290 
  291         return (error);
  292 }
  293 
  294 SYSCTL_DECL(_net_inet_tcp_cc_vegas);
  295 SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, vegas, CTLFLAG_RW, NULL,
  296     "Vegas related settings");
  297 
  298 SYSCTL_VNET_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, alpha,
  299     CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(vegas_alpha), 1, &vegas_alpha_handler,
  300     "IU", "vegas alpha, specified as number of \"buffers\" (0 < alpha < beta)");
  301 
  302 SYSCTL_VNET_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, beta,
  303     CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(vegas_beta), 3, &vegas_beta_handler,
  304     "IU", "vegas beta, specified as number of \"buffers\" (0 < alpha < beta)");
  305 
  306 DECLARE_CC_MODULE(vegas, &vegas_cc_algo);
  307 MODULE_DEPEND(vegas, ertt, 1, 1, 1);
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FreeBSD/Linux Kernel Cross Reference sys/netinet/cc/cc_vegas.c

FreeBSD/Linux Kernel Cross Reference
sys/netinet/cc/cc_vegas.c
