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freebsd-dev/sys/netinet/cc/cc_cdg.c
Hiren Panchasara e04310d59b Set slow start threshold more accurately on loss to be flightsize/2 instead of 
cwnd/2 as recommended by RFC5681. (spotted by mmacy at nextbsd dot org)

Restore pre-r307901 behavior of aligning ssthresh/cwnd on mss boundary. (spotted
by slawa at zxy dot spb dot ru)

Tested by:	    dim, Slawa <slawa at zxy dot spb dot ru>
MFC after:	    1 month
X-MFC with:	    r307901
Sponsored by:	    Limelight Networks
Differential Revision:	https://reviews.freebsd.org/D8349
2016-11-01 21:08:37 +00:00

711 lines
23 KiB
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/*-
* Copyright (c) 2009-2013
* Swinburne University of Technology, Melbourne, Australia
* All rights reserved.
*
* This software was developed at the Centre for Advanced Internet
* Architectures, Swinburne University of Technology, by David Hayes, made
* possible in part by a gift from The Cisco University Research Program Fund,
* a corporate advised fund of Silicon Valley Community Foundation. Development
* and testing were further assisted by a grant 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.
*/
/*
* CAIA Delay-Gradient (CDG) congestion control algorithm
*
* An implemention of the delay-gradient congestion control algorithm proposed
* in the following paper:
*
* D. A. Hayes and G. Armitage, "Revisiting TCP Congestion Control using Delay
* Gradients", in IFIP Networking, Valencia, Spain, 9-13 May 2011.
*
* Developed as part of the NewTCP research project at Swinburne University of
* Technology's Centre for Advanced Internet Architectures, Melbourne,
* Australia. More details are available at:
* http://caia.swin.edu.au/urp/newtcp/
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/hhook.h>
#include <sys/kernel.h>
#include <sys/khelp.h>
#include <sys/limits.h>
#include <sys/lock.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/vnet.h>
#include <netinet/tcp.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/cc/cc.h>
#include <netinet/cc/cc_module.h>
#include <netinet/khelp/h_ertt.h>
#include <vm/uma.h>
#define CDG_VERSION "0.1"
#define CAST_PTR_INT(X) (*((int*)(X)))
/* Private delay-gradient induced congestion control signal. */
#define CC_CDG_DELAY 0x01000000
/* NewReno window deflation factor on loss (as a percentage). */
#define RENO_BETA 50
/* Queue states. */
#define CDG_Q_EMPTY 1
#define CDG_Q_RISING 2
#define CDG_Q_FALLING 3
#define CDG_Q_FULL 4
#define CDG_Q_UNKNOWN 9999
/* Number of bit shifts used in probexp lookup table. */
#define EXP_PREC 15
/* Largest gradient represented in probexp lookup table. */
#define MAXGRAD 5
/*
* Delay Precision Enhance - number of bit shifts used for qtrend related
* integer arithmetic precision.
*/
#define D_P_E 7
struct qdiff_sample {
long qdiff;
STAILQ_ENTRY(qdiff_sample) qdiff_lnk;
};
struct cdg {
long max_qtrend;
long min_qtrend;
STAILQ_HEAD(minrtts_head, qdiff_sample) qdiffmin_q;
STAILQ_HEAD(maxrtts_head, qdiff_sample) qdiffmax_q;
long window_incr;
/* rttcount for window increase when in congestion avoidance */
long rtt_count;
/* maximum measured rtt within an rtt period */
int maxrtt_in_rtt;
/* maximum measured rtt within prev rtt period */
int maxrtt_in_prevrtt;
/* minimum measured rtt within an rtt period */
int minrtt_in_rtt;
/* minimum measured rtt within prev rtt period */
int minrtt_in_prevrtt;
/* consecutive congestion episode counter */
uint32_t consec_cong_cnt;
/* when tracking a new reno type loss window */
uint32_t shadow_w;
/* maximum number of samples in the moving average queue */
int sample_q_size;
/* number of samples in the moving average queue */
int num_samples;
/* estimate of the queue state of the path */
int queue_state;
};
/*
* Lookup table for:
* (1 - exp(-x)) << EXP_PREC, where x = [0,MAXGRAD] in 2^-7 increments
*
* Note: probexp[0] is set to 10 (not 0) as a safety for very low increase
* gradients.
*/
static const int probexp[641] = {
10,255,508,759,1008,1255,1501,1744,1985,2225,2463,2698,2932,3165,3395,3624,
3850,4075,4299,4520,4740,4958,5175,5389,5602,5814,6024,6232,6438,6643,6846,
7048,7248,7447,7644,7839,8033,8226,8417,8606,8794,8981,9166,9350,9532,9713,
9892,10070,10247,10422,10596,10769,10940,11110,11278,11445,11611,11776,11939,
12101,12262,12422,12580,12737,12893,13048,13201,13354,13505,13655,13803,13951,
14097,14243,14387,14530,14672,14813,14952,15091,15229,15365,15500,15635,15768,
15900,16032,16162,16291,16419,16547,16673,16798,16922,17046,17168,17289,17410,
17529,17648,17766,17882,17998,18113,18227,18340,18453,18564,18675,18784,18893,
19001,19108,19215,19320,19425,19529,19632,19734,19835,19936,20036,20135,20233,
20331,20427,20523,20619,20713,20807,20900,20993,21084,21175,21265,21355,21444,
21532,21619,21706,21792,21878,21962,22046,22130,22213,22295,22376,22457,22537,
22617,22696,22774,22852,22929,23006,23082,23157,23232,23306,23380,23453,23525,
23597,23669,23739,23810,23879,23949,24017,24085,24153,24220,24286,24352,24418,
24483,24547,24611,24675,24738,24800,24862,24924,24985,25045,25106,25165,25224,
25283,25341,25399,25456,25513,25570,25626,25681,25737,25791,25846,25899,25953,
26006,26059,26111,26163,26214,26265,26316,26366,26416,26465,26514,26563,26611,
26659,26707,26754,26801,26847,26893,26939,26984,27029,27074,27118,27162,27206,
27249,27292,27335,27377,27419,27460,27502,27543,27583,27624,27664,27703,27743,
27782,27821,27859,27897,27935,27973,28010,28047,28084,28121,28157,28193,28228,
28263,28299,28333,28368,28402,28436,28470,28503,28536,28569,28602,28634,28667,
28699,28730,28762,28793,28824,28854,28885,28915,28945,28975,29004,29034,29063,
29092,29120,29149,29177,29205,29232,29260,29287,29314,29341,29368,29394,29421,
29447,29472,29498,29524,29549,29574,29599,29623,29648,29672,29696,29720,29744,
29767,29791,29814,29837,29860,29882,29905,29927,29949,29971,29993,30014,30036,
30057,30078,30099,30120,30141,30161,30181,30201,30221,30241,30261,30280,30300,
30319,30338,30357,30376,30394,30413,30431,30449,30467,30485,30503,30521,30538,
30555,30573,30590,30607,30624,30640,30657,30673,30690,30706,30722,30738,30753,
30769,30785,30800,30815,30831,30846,30861,30876,30890,30905,30919,30934,30948,
30962,30976,30990,31004,31018,31031,31045,31058,31072,31085,31098,31111,31124,
31137,31149,31162,31174,31187,31199,31211,31223,31235,31247,31259,31271,31283,
31294,31306,31317,31328,31339,31351,31362,31373,31383,31394,31405,31416,31426,
31436,31447,31457,31467,31477,31487,31497,31507,31517,31527,31537,31546,31556,
31565,31574,31584,31593,31602,31611,31620,31629,31638,31647,31655,31664,31673,
31681,31690,31698,31706,31715,31723,31731,31739,31747,31755,31763,31771,31778,
31786,31794,31801,31809,31816,31824,31831,31838,31846,31853,31860,31867,31874,
31881,31888,31895,31902,31908,31915,31922,31928,31935,31941,31948,31954,31960,
31967,31973,31979,31985,31991,31997,32003,32009,32015,32021,32027,32033,32038,
32044,32050,32055,32061,32066,32072,32077,32083,32088,32093,32098,32104,32109,
32114,32119,32124,32129,32134,32139,32144,32149,32154,32158,32163,32168,32173,
32177,32182,32186,32191,32195,32200,32204,32209,32213,32217,32222,32226,32230,
32234,32238,32242,32247,32251,32255,32259,32263,32267,32270,32274,32278,32282,
32286,32290,32293,32297,32301,32304,32308,32311,32315,32318,32322,32325,32329,
32332,32336,32339,32342,32346,32349,32352,32356,32359,32362,32365,32368,32371,
32374,32377,32381,32384,32387,32389,32392,32395,32398,32401,32404,32407,32410,
32412,32415,32418,32421,32423,32426,32429,32431,32434,32437,32439,32442,32444,
32447,32449,32452,32454,32457,32459,32461,32464,32466,32469,32471,32473,32476,
32478,32480,32482,32485,32487,32489,32491,32493,32495,32497,32500,32502,32504,
32506,32508,32510,32512,32514,32516,32518,32520,32522,32524,32526,32527,32529,
32531,32533,32535,32537,32538,32540,32542,32544,32545,32547};
static uma_zone_t qdiffsample_zone;
static MALLOC_DEFINE(M_CDG, "cdg data",
"Per connection data required for the CDG congestion control algorithm");
static int ertt_id;
static VNET_DEFINE(uint32_t, cdg_alpha_inc);
static VNET_DEFINE(uint32_t, cdg_beta_delay);
static VNET_DEFINE(uint32_t, cdg_beta_loss);
static VNET_DEFINE(uint32_t, cdg_smoothing_factor);
static VNET_DEFINE(uint32_t, cdg_exp_backoff_scale);
static VNET_DEFINE(uint32_t, cdg_consec_cong);
static VNET_DEFINE(uint32_t, cdg_hold_backoff);
#define V_cdg_alpha_inc VNET(cdg_alpha_inc)
#define V_cdg_beta_delay VNET(cdg_beta_delay)
#define V_cdg_beta_loss VNET(cdg_beta_loss)
#define V_cdg_smoothing_factor VNET(cdg_smoothing_factor)
#define V_cdg_exp_backoff_scale VNET(cdg_exp_backoff_scale)
#define V_cdg_consec_cong VNET(cdg_consec_cong)
#define V_cdg_hold_backoff VNET(cdg_hold_backoff)
/* Function prototypes. */
static int cdg_mod_init(void);
static int cdg_mod_destroy(void);
static void cdg_conn_init(struct cc_var *ccv);
static int cdg_cb_init(struct cc_var *ccv);
static void cdg_cb_destroy(struct cc_var *ccv);
static void cdg_cong_signal(struct cc_var *ccv, uint32_t signal_type);
static void cdg_ack_received(struct cc_var *ccv, uint16_t ack_type);
struct cc_algo cdg_cc_algo = {
.name = "cdg",
.mod_init = cdg_mod_init,
.ack_received = cdg_ack_received,
.cb_destroy = cdg_cb_destroy,
.cb_init = cdg_cb_init,
.conn_init = cdg_conn_init,
.cong_signal = cdg_cong_signal,
.mod_destroy = cdg_mod_destroy
};
/* Vnet created and being initialised. */
static void
cdg_init_vnet(const void *unused __unused)
{
V_cdg_alpha_inc = 0;
V_cdg_beta_delay = 70;
V_cdg_beta_loss = 50;
V_cdg_smoothing_factor = 8;
V_cdg_exp_backoff_scale = 3;
V_cdg_consec_cong = 5;
V_cdg_hold_backoff = 5;
}
static int
cdg_mod_init(void)
{
VNET_ITERATOR_DECL(v);
ertt_id = khelp_get_id("ertt");
if (ertt_id <= 0)
return (EINVAL);
qdiffsample_zone = uma_zcreate("cdg_qdiffsample",
sizeof(struct qdiff_sample), NULL, NULL, NULL, NULL, 0, 0);
VNET_LIST_RLOCK();
VNET_FOREACH(v) {
CURVNET_SET(v);
cdg_init_vnet(NULL);
CURVNET_RESTORE();
}
VNET_LIST_RUNLOCK();
cdg_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
cdg_cc_algo.after_idle = newreno_cc_algo.after_idle;
return (0);
}
static int
cdg_mod_destroy(void)
{
uma_zdestroy(qdiffsample_zone);
return (0);
}
static int
cdg_cb_init(struct cc_var *ccv)
{
struct cdg *cdg_data;
cdg_data = malloc(sizeof(struct cdg), M_CDG, M_NOWAIT);
if (cdg_data == NULL)
return (ENOMEM);
cdg_data->shadow_w = 0;
cdg_data->max_qtrend = 0;
cdg_data->min_qtrend = 0;
cdg_data->queue_state = CDG_Q_UNKNOWN;
cdg_data->maxrtt_in_rtt = 0;
cdg_data->maxrtt_in_prevrtt = 0;
cdg_data->minrtt_in_rtt = INT_MAX;
cdg_data->minrtt_in_prevrtt = 0;
cdg_data->window_incr = 0;
cdg_data->rtt_count = 0;
cdg_data->consec_cong_cnt = 0;
cdg_data->sample_q_size = V_cdg_smoothing_factor;
cdg_data->num_samples = 0;
STAILQ_INIT(&cdg_data->qdiffmin_q);
STAILQ_INIT(&cdg_data->qdiffmax_q);
ccv->cc_data = cdg_data;
return (0);
}
static void
cdg_conn_init(struct cc_var *ccv)
{
struct cdg *cdg_data = ccv->cc_data;
/*
* Initialise the shadow_cwnd in case we are competing with loss based
* flows from the start
*/
cdg_data->shadow_w = CCV(ccv, snd_cwnd);
}
static void
cdg_cb_destroy(struct cc_var *ccv)
{
struct cdg *cdg_data;
struct qdiff_sample *qds, *qds_n;
cdg_data = ccv->cc_data;
qds = STAILQ_FIRST(&cdg_data->qdiffmin_q);
while (qds != NULL) {
qds_n = STAILQ_NEXT(qds, qdiff_lnk);
uma_zfree(qdiffsample_zone,qds);
qds = qds_n;
}
qds = STAILQ_FIRST(&cdg_data->qdiffmax_q);
while (qds != NULL) {
qds_n = STAILQ_NEXT(qds, qdiff_lnk);
uma_zfree(qdiffsample_zone,qds);
qds = qds_n;
}
free(ccv->cc_data, M_CDG);
}
static int
cdg_beta_handler(SYSCTL_HANDLER_ARGS)
{
if (req->newptr != NULL &&
(CAST_PTR_INT(req->newptr) == 0 || CAST_PTR_INT(req->newptr) > 100))
return (EINVAL);
return (sysctl_handle_int(oidp, arg1, arg2, req));
}
static int
cdg_exp_backoff_scale_handler(SYSCTL_HANDLER_ARGS)
{
if (req->newptr != NULL && CAST_PTR_INT(req->newptr) < 1)
return (EINVAL);
return (sysctl_handle_int(oidp, arg1, arg2, req));
}
static inline uint32_t
cdg_window_decrease(struct cc_var *ccv, unsigned long owin, unsigned int beta)
{
return ((ulmin(CCV(ccv, snd_wnd), owin) * beta) / 100);
}
/*
* Window increase function
* This window increase function is independent of the initial window size
* to ensure small window flows are not discriminated against (i.e. fairness).
* It increases at 1pkt/rtt like Reno for alpha_inc rtts, and then 2pkts/rtt for
* the next alpha_inc rtts, etc.
*/
static void
cdg_window_increase(struct cc_var *ccv, int new_measurement)
{
struct cdg *cdg_data;
int incr, s_w_incr;
cdg_data = ccv->cc_data;
incr = s_w_incr = 0;
if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh)) {
/* Slow start. */
incr = CCV(ccv, t_maxseg);
s_w_incr = incr;
cdg_data->window_incr = cdg_data->rtt_count = 0;
} else {
/* Congestion avoidance. */
if (new_measurement) {
s_w_incr = CCV(ccv, t_maxseg);
if (V_cdg_alpha_inc == 0) {
incr = CCV(ccv, t_maxseg);
} else {
if (++cdg_data->rtt_count >= V_cdg_alpha_inc) {
cdg_data->window_incr++;
cdg_data->rtt_count = 0;
}
incr = CCV(ccv, t_maxseg) *
cdg_data->window_incr;
}
}
}
if (cdg_data->shadow_w > 0)
cdg_data->shadow_w = ulmin(cdg_data->shadow_w + s_w_incr,
TCP_MAXWIN << CCV(ccv, snd_scale));
CCV(ccv, snd_cwnd) = ulmin(CCV(ccv, snd_cwnd) + incr,
TCP_MAXWIN << CCV(ccv, snd_scale));
}
static void
cdg_cong_signal(struct cc_var *ccv, uint32_t signal_type)
{
struct cdg *cdg_data = ccv->cc_data;
uint32_t cwin;
u_int mss;
cwin = CCV(ccv, snd_cwnd);
mss = CCV(ccv, t_maxseg);
switch(signal_type) {
case CC_CDG_DELAY:
CCV(ccv, snd_ssthresh) = cdg_window_decrease(ccv,
CCV(ccv, snd_cwnd), V_cdg_beta_delay);
CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
CCV(ccv, snd_recover) = CCV(ccv, snd_max);
cdg_data->window_incr = cdg_data->rtt_count = 0;
ENTER_CONGRECOVERY(CCV(ccv, t_flags));
break;
case CC_NDUPACK:
/*
* If already responding to congestion OR we have guessed no
* queue in the path is full.
*/
if (IN_CONGRECOVERY(CCV(ccv, t_flags)) ||
cdg_data->queue_state < CDG_Q_FULL) {
CCV(ccv, snd_ssthresh) = cwin;
CCV(ccv, snd_recover) = CCV(ccv, snd_max);
} else {
/*
* Loss is likely to be congestion related. We have
* inferred a queue full state, so have shadow window
* react to loss as NewReno would.
*/
if (cdg_data->shadow_w > 0)
cdg_data->shadow_w = cdg_window_decrease(ccv,
cdg_data->shadow_w, RENO_BETA);
CCV(ccv, snd_ssthresh) = max(cdg_data->shadow_w,
cdg_window_decrease(ccv, cwin, V_cdg_beta_loss));
CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
cdg_data->window_incr = cdg_data->rtt_count = 0;
}
ENTER_RECOVERY(CCV(ccv, t_flags));
break;
case CC_RTO:
CCV(ccv, snd_ssthresh) =
max((CCV(ccv, snd_max) - CCV(ccv, snd_una)) / 2 / mss, 2)
* mss;
CCV(ccv, snd_cwnd) = mss;
break;
default:
newreno_cc_algo.cong_signal(ccv, signal_type);
break;
}
}
/*
* Using a negative exponential probabilistic backoff so that sources with
* varying RTTs which share the same link will, on average, have the same
* probability of backoff over time.
*
* Prob_backoff = 1 - exp(-qtrend / V_cdg_exp_backoff_scale), where
* V_cdg_exp_backoff_scale is the average qtrend for the exponential backoff.
*/
static inline int
prob_backoff(long qtrend)
{
int backoff, idx, p;
backoff = (qtrend > ((MAXGRAD * V_cdg_exp_backoff_scale) << D_P_E));
if (!backoff) {
if (V_cdg_exp_backoff_scale > 1)
idx = (qtrend + V_cdg_exp_backoff_scale / 2) /
V_cdg_exp_backoff_scale;
else
idx = qtrend;
/* Backoff probability proportional to rate of queue growth. */
p = (INT_MAX / (1 << EXP_PREC)) * probexp[idx];
backoff = (random() < p);
}
return (backoff);
}
static inline void
calc_moving_average(struct cdg *cdg_data, long qdiff_max, long qdiff_min)
{
struct qdiff_sample *qds;
++cdg_data->num_samples;
if (cdg_data->num_samples > cdg_data->sample_q_size) {
/* Minimum RTT. */
qds = STAILQ_FIRST(&cdg_data->qdiffmin_q);
cdg_data->min_qtrend = cdg_data->min_qtrend +
(qdiff_min - qds->qdiff) / cdg_data->sample_q_size;
STAILQ_REMOVE_HEAD(&cdg_data->qdiffmin_q, qdiff_lnk);
qds->qdiff = qdiff_min;
STAILQ_INSERT_TAIL(&cdg_data->qdiffmin_q, qds, qdiff_lnk);
/* Maximum RTT. */
qds = STAILQ_FIRST(&cdg_data->qdiffmax_q);
cdg_data->max_qtrend = cdg_data->max_qtrend +
(qdiff_max - qds->qdiff) / cdg_data->sample_q_size;
STAILQ_REMOVE_HEAD(&cdg_data->qdiffmax_q, qdiff_lnk);
qds->qdiff = qdiff_max;
STAILQ_INSERT_TAIL(&cdg_data->qdiffmax_q, qds, qdiff_lnk);
--cdg_data->num_samples;
} else {
qds = uma_zalloc(qdiffsample_zone, M_NOWAIT);
if (qds != NULL) {
cdg_data->min_qtrend = cdg_data->min_qtrend +
qdiff_min / cdg_data->sample_q_size;
qds->qdiff = qdiff_min;
STAILQ_INSERT_TAIL(&cdg_data->qdiffmin_q, qds,
qdiff_lnk);
}
qds = uma_zalloc(qdiffsample_zone, M_NOWAIT);
if (qds) {
cdg_data->max_qtrend = cdg_data->max_qtrend +
qdiff_max / cdg_data->sample_q_size;
qds->qdiff = qdiff_max;
STAILQ_INSERT_TAIL(&cdg_data->qdiffmax_q, qds,
qdiff_lnk);
}
}
}
static void
cdg_ack_received(struct cc_var *ccv, uint16_t ack_type)
{
struct cdg *cdg_data;
struct ertt *e_t;
long qdiff_max, qdiff_min;
int congestion, new_measurement, slowstart;
cdg_data = ccv->cc_data;
e_t = (struct ertt *)khelp_get_osd(CCV(ccv, osd), ertt_id);
new_measurement = e_t->flags & ERTT_NEW_MEASUREMENT;
congestion = 0;
cdg_data->maxrtt_in_rtt = imax(e_t->rtt, cdg_data->maxrtt_in_rtt);
cdg_data->minrtt_in_rtt = imin(e_t->rtt, cdg_data->minrtt_in_rtt);
if (new_measurement) {
slowstart = (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh));
/*
* Update smoothed gradient measurements. Since we are only
* using one measurement per RTT, use max or min rtt_in_rtt.
* This is also less noisy than a sample RTT measurement. Max
* RTT measurements can have trouble due to OS issues.
*/
if (cdg_data->maxrtt_in_prevrtt) {
qdiff_max = ((long)(cdg_data->maxrtt_in_rtt -
cdg_data->maxrtt_in_prevrtt) << D_P_E );
qdiff_min = ((long)(cdg_data->minrtt_in_rtt -
cdg_data->minrtt_in_prevrtt) << D_P_E );
calc_moving_average(cdg_data, qdiff_max, qdiff_min);
/* Probabilistic backoff with respect to gradient. */
if (slowstart && qdiff_min > 0)
congestion = prob_backoff(qdiff_min);
else if (cdg_data->min_qtrend > 0)
congestion = prob_backoff(cdg_data->min_qtrend);
else if (slowstart && qdiff_max > 0)
congestion = prob_backoff(qdiff_max);
else if (cdg_data->max_qtrend > 0)
congestion = prob_backoff(cdg_data->max_qtrend);
/* Update estimate of queue state. */
if (cdg_data->min_qtrend > 0 &&
cdg_data->max_qtrend <= 0) {
cdg_data->queue_state = CDG_Q_FULL;
} else if (cdg_data->min_qtrend >= 0 &&
cdg_data->max_qtrend < 0) {
cdg_data->queue_state = CDG_Q_EMPTY;
cdg_data->shadow_w = 0;
} else if (cdg_data->min_qtrend > 0 &&
cdg_data->max_qtrend > 0) {
cdg_data->queue_state = CDG_Q_RISING;
} else if (cdg_data->min_qtrend < 0 &&
cdg_data->max_qtrend < 0) {
cdg_data->queue_state = CDG_Q_FALLING;
}
if (cdg_data->min_qtrend < 0 ||
cdg_data->max_qtrend < 0)
cdg_data->consec_cong_cnt = 0;
}
cdg_data->minrtt_in_prevrtt = cdg_data->minrtt_in_rtt;
cdg_data->minrtt_in_rtt = INT_MAX;
cdg_data->maxrtt_in_prevrtt = cdg_data->maxrtt_in_rtt;
cdg_data->maxrtt_in_rtt = 0;
e_t->flags &= ~ERTT_NEW_MEASUREMENT;
}
if (congestion) {
cdg_data->consec_cong_cnt++;
if (!IN_RECOVERY(CCV(ccv, t_flags))) {
if (cdg_data->consec_cong_cnt <= V_cdg_consec_cong)
cdg_cong_signal(ccv, CC_CDG_DELAY);
else
/*
* We have been backing off but the queue is not
* falling. Assume we are competing with
* loss-based flows and don't back off for the
* next V_cdg_hold_backoff RTT periods.
*/
if (cdg_data->consec_cong_cnt >=
V_cdg_consec_cong + V_cdg_hold_backoff)
cdg_data->consec_cong_cnt = 0;
/* Won't see effect until 2nd RTT. */
cdg_data->maxrtt_in_prevrtt = 0;
/*
* Resync shadow window in case we are competing with a
* loss based flow
*/
cdg_data->shadow_w = ulmax(CCV(ccv, snd_cwnd),
cdg_data->shadow_w);
}
} else if (ack_type == CC_ACK)
cdg_window_increase(ccv, new_measurement);
}
/* When a vnet is created and being initialised, init the per-stack CDG vars. */
VNET_SYSINIT(cdg_init_vnet, SI_SUB_PROTO_BEGIN, SI_ORDER_FIRST,
cdg_init_vnet, NULL);
SYSCTL_DECL(_net_inet_tcp_cc_cdg);
SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, cdg, CTLFLAG_RW, NULL,
"CAIA delay-gradient congestion control related settings");
SYSCTL_STRING(_net_inet_tcp_cc_cdg, OID_AUTO, version,
CTLFLAG_RD, CDG_VERSION, sizeof(CDG_VERSION) - 1,
"Current algorithm/implementation version number");
SYSCTL_UINT(_net_inet_tcp_cc_cdg, OID_AUTO, alpha_inc,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(cdg_alpha_inc), 0,
"Increment the window increase factor alpha by 1 MSS segment every "
"alpha_inc RTTs during congestion avoidance mode.");
SYSCTL_PROC(_net_inet_tcp_cc_cdg, OID_AUTO, beta_delay,
CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW, &VNET_NAME(cdg_beta_delay), 70,
&cdg_beta_handler, "IU",
"Delay-based window decrease factor as a percentage "
"(on delay-based backoff, w = w * beta_delay / 100)");
SYSCTL_PROC(_net_inet_tcp_cc_cdg, OID_AUTO, beta_loss,
CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW, &VNET_NAME(cdg_beta_loss), 50,
&cdg_beta_handler, "IU",
"Loss-based window decrease factor as a percentage "
"(on loss-based backoff, w = w * beta_loss / 100)");
SYSCTL_PROC(_net_inet_tcp_cc_cdg, OID_AUTO, exp_backoff_scale,
CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW,
&VNET_NAME(cdg_exp_backoff_scale), 2, &cdg_exp_backoff_scale_handler, "IU",
"Scaling parameter for the probabilistic exponential backoff");
SYSCTL_UINT(_net_inet_tcp_cc_cdg, OID_AUTO, smoothing_factor,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(cdg_smoothing_factor), 8,
"Number of samples used for moving average smoothing (0 = no smoothing)");
SYSCTL_UINT(_net_inet_tcp_cc_cdg, OID_AUTO, loss_compete_consec_cong,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(cdg_consec_cong), 5,
"Number of consecutive delay-gradient based congestion episodes which will "
"trigger loss based CC compatibility");
SYSCTL_UINT(_net_inet_tcp_cc_cdg, OID_AUTO, loss_compete_hold_backoff,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(cdg_hold_backoff), 5,
"Number of consecutive delay-gradient based congestion episodes to hold "
"the window backoff for loss based CC compatibility");
DECLARE_CC_MODULE(cdg, &cdg_cc_algo);
MODULE_DEPEND(cdg, ertt, 1, 1, 1);
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