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Import a clean-room implementation of the VEGAS congestion control algorithm

Browse Source 
based on the paper "TCP Vegas: end to end congestion avoidance on a global
internet" by Brakmo and Peterson. It is implemented as a kernel module
compatible with the recently committed modular congestion control framework.

VEGAS uses network delay as a congestion indicator and unlike regular loss-based
algorithms, attempts to keep the network operating with stable queuing delays
and no congestion losses. By keeping network buffers used along the path within
a set range, queuing delays are kept low while maintaining high throughput.

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
This commit is contained in:
Lawrence Stewart 2011-02-01 06:17:00 +00:00
parent 29e9b81e77
commit 1d4ed791d0
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=218152
3 changed files with 319 additions and 1 deletions
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3
sys/modules/cc/Makefile
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@ -1,6 +1,7 @@
# $FreeBSD$
SUBDIR= cc_cubic \
cc_htcp
cc_htcp \
cc_vegas
.include <bsd.subdir.mk>

9
sys/modules/cc/cc_vegas/Makefile Normal file
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@ -0,0 +1,9 @@
# $FreeBSD$
.include <bsd.own.mk>
.PATH: ${.CURDIR}/../../../netinet/cc
KMOD= cc_vegas
SRCS= cc_vegas.c
.include <bsd.kmod.mk>

308
sys/netinet/cc/cc_vegas.c Normal file
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@ -0,0 +1,308 @@
/*-
* Copyright (c) 2009-2010
* Swinburne University of Technology, Melbourne, Australia
* Copyright (c) 2010 Lawrence Stewart <lstewart@freebsd.org>
* 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 Vegas congestion control algorithm for FreeBSD,
* based on L. S. Brakmo and L. L. Peterson, "TCP Vegas: end to end congestion
* avoidance on a global internet", IEEE J. Sel. Areas Commun., vol. 13, no. 8,
* pp. 1465-1480, Oct. 1995. The original Vegas duplicate ack policy has not
* been implemented, since clock ticks are not as course as they were (i.e.
* 500ms) when Vegas was designed. Also, packets are timed once per RTT as in
* the original paper.
*
* 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/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_VEGAS_RATE 0x01000000
static void vegas_ack_received(struct cc_var *ccv, uint16_t ack_type);
static void vegas_cb_destroy(struct cc_var *ccv);
static int vegas_cb_init(struct cc_var *ccv);
static void vegas_cong_signal(struct cc_var *ccv, uint32_t signal_type);
static void vegas_conn_init(struct cc_var *ccv);
static int vegas_mod_init(void);
struct vegas {
int slow_start_toggle;
};
static int32_t ertt_id;
static VNET_DEFINE(uint32_t, vegas_alpha) = 1;
static VNET_DEFINE(uint32_t, vegas_beta) = 3;
#define V_vegas_alpha VNET(vegas_alpha)
#define V_vegas_beta VNET(vegas_beta)
MALLOC_DECLARE(M_VEGAS);
MALLOC_DEFINE(M_VEGAS, "vegas data",
"Per connection data required for the Vegas congestion control algorithm");
struct cc_algo vegas_cc_algo = {
.name = "vegas",
.ack_received = vegas_ack_received,
.cb_destroy = vegas_cb_destroy,
.cb_init = vegas_cb_init,
.cong_signal = vegas_cong_signal,
.conn_init = vegas_conn_init,
.mod_init = vegas_mod_init
};
/*
* The vegas window adjustment is done once every RTT, as indicated by the
* ERTT_NEW_MEASUREMENT flag. This flag is reset once the new measurment data
* has been used.
*/
static void
vegas_ack_received(struct cc_var *ccv, uint16_t ack_type)
{
struct ertt *e_t;
struct vegas *vegas_data;
long actual_tx_rate, expected_tx_rate, ndiff;
e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
vegas_data = ccv->cc_data;
if (e_t->flags & ERTT_NEW_MEASUREMENT) { /* Once per RTT. */
if (e_t->minrtt && e_t->markedpkt_rtt) {
expected_tx_rate = e_t->marked_snd_cwnd / e_t->minrtt;
actual_tx_rate = e_t->bytes_tx_in_marked_rtt /
e_t->markedpkt_rtt;
ndiff = (expected_tx_rate - actual_tx_rate) *
e_t->minrtt / CCV(ccv, t_maxseg);
if (ndiff < V_vegas_alpha) {
if (CCV(ccv, snd_cwnd) <=
CCV(ccv, snd_ssthresh)) {
vegas_data->slow_start_toggle =
vegas_data->slow_start_toggle ?
0 : 1;
} else {
vegas_data->slow_start_toggle = 0;
CCV(ccv, snd_cwnd) =
min(CCV(ccv, snd_cwnd) +
CCV(ccv, t_maxseg),
TCP_MAXWIN << CCV(ccv, snd_scale));
}
} else if (ndiff > V_vegas_beta) {
/* Rate-based congestion. */
vegas_cong_signal(ccv, CC_VEGAS_RATE);
vegas_data->slow_start_toggle = 0;
}
}
e_t->flags &= ~ERTT_NEW_MEASUREMENT;
}
if (vegas_data->slow_start_toggle)
newreno_cc_algo.ack_received(ccv, ack_type);
}
static void
vegas_cb_destroy(struct cc_var *ccv)
{
if (ccv->cc_data != NULL)
free(ccv->cc_data, M_VEGAS);
}
static int
vegas_cb_init(struct cc_var *ccv)
{
struct vegas *vegas_data;
vegas_data = malloc(sizeof(struct vegas), M_VEGAS, M_NOWAIT);
if (vegas_data == NULL)
return (ENOMEM);
vegas_data->slow_start_toggle = 1;
ccv->cc_data = vegas_data;
return (0);
}
/*
* If congestion has been triggered triggered by the Vegas measured rates, it is
* handled here, otherwise it falls back to newreno's congestion handling.
*/
static void
vegas_cong_signal(struct cc_var *ccv, uint32_t signal_type)
{
struct vegas *vegas_data;
int presignalrecov;
vegas_data = ccv->cc_data;
if (IN_RECOVERY(CCV(ccv, t_flags)))
presignalrecov = 1;
else
presignalrecov = 0;
switch(signal_type) {
case CC_VEGAS_RATE:
if (!IN_RECOVERY(CCV(ccv, t_flags))) {
CCV(ccv, snd_cwnd) = max(2 * CCV(ccv, t_maxseg),
CCV(ccv, snd_cwnd) - CCV(ccv, t_maxseg));
if (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh))
/* Exit slow start. */
CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
}
break;
default:
newreno_cc_algo.cong_signal(ccv, signal_type);
}
if (IN_RECOVERY(CCV(ccv, t_flags)) && !presignalrecov)
vegas_data->slow_start_toggle =
(CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh)) ? 1 : 0;
}
static void
vegas_conn_init(struct cc_var *ccv)
{
struct vegas *vegas_data;
vegas_data = ccv->cc_data;
vegas_data->slow_start_toggle = 1;
}
static int
vegas_mod_init(void)
{
ertt_id = khelp_get_id("ertt");
if (ertt_id <= 0) {
printf("%s: h_ertt module not found\n", __func__);
return (ENOENT);
}
vegas_cc_algo.after_idle = newreno_cc_algo.after_idle;
vegas_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
return (0);
}
static int
vegas_alpha_handler(SYSCTL_HANDLER_ARGS)
{
int error;
uint32_t new;
new = V_vegas_alpha;
error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr != NULL) {
if (CAST_PTR_INT(req->newptr) < 1 ||
CAST_PTR_INT(req->newptr) > V_vegas_beta)
error = EINVAL;
else
V_vegas_alpha = new;
}
return (error);
}
static int
vegas_beta_handler(SYSCTL_HANDLER_ARGS)
{
int error;
uint32_t new;
new = V_vegas_beta;
error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr != NULL) {
if (CAST_PTR_INT(req->newptr) < 1 ||
CAST_PTR_INT(req->newptr) < V_vegas_alpha)
error = EINVAL;
else
V_vegas_beta = new;
}
return (error);
}
SYSCTL_DECL(_net_inet_tcp_cc_vegas);
SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, vegas, CTLFLAG_RW, NULL,
"Vegas related settings");
SYSCTL_VNET_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, alpha,
CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(vegas_alpha), 1, &vegas_alpha_handler,
"IU", "vegas alpha, specified as number of \"buffers\" (0 < alpha < beta)");
SYSCTL_VNET_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, beta,
CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(vegas_beta), 3, &vegas_beta_handler,
"IU", "vegas beta, specified as number of \"buffers\" (0 < alpha < beta)");
DECLARE_CC_MODULE(vegas, &vegas_cc_algo);
MODULE_DEPEND(vegas, ertt, 1, 1, 1);