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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 | #ifndef __NET_SCHED_CODEL_H
#define __NET_SCHED_CODEL_H
/*
* Codel - The Controlled-Delay Active Queue Management algorithm
*
* Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
* Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
* Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
* Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
*
* 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,
* without modification.
* 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.
* 3. The names of the authors may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* Alternatively, provided that this notice is retained in full, this
* software may be distributed under the terms of the GNU General
* Public License ("GPL") version 2, in which case the provisions of the
* GPL apply INSTEAD OF those given above.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT
* OWNER 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.
*
*/
#include <linux/types.h>
#include <linux/ktime.h>
#include <linux/skbuff.h>
#include <net/pkt_sched.h>
#include <net/inet_ecn.h>
/* Controlling Queue Delay (CoDel) algorithm
* =========================================
* Source : Kathleen Nichols and Van Jacobson
* http://queue.acm.org/detail.cfm?id=2209336
*
* Implemented on linux by Dave Taht and Eric Dumazet
*/
/* CoDel uses a 1024 nsec clock, encoded in u32
* This gives a range of 2199 seconds, because of signed compares
*/
typedef u32 codel_time_t;
typedef s32 codel_tdiff_t;
#define CODEL_SHIFT 10
#define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT)
static inline codel_time_t codel_get_time(void)
{
u64 ns = ktime_get_ns();
return ns >> CODEL_SHIFT;
}
/* Dealing with timer wrapping, according to RFC 1982, as desc in wikipedia:
* https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
* codel_time_after(a,b) returns true if the time a is after time b.
*/
#define codel_time_after(a, b) \
(typecheck(codel_time_t, a) && \
typecheck(codel_time_t, b) && \
((s32)((a) - (b)) > 0))
#define codel_time_before(a, b) codel_time_after(b, a)
#define codel_time_after_eq(a, b) \
(typecheck(codel_time_t, a) && \
typecheck(codel_time_t, b) && \
((s32)((a) - (b)) >= 0))
#define codel_time_before_eq(a, b) codel_time_after_eq(b, a)
/* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */
struct codel_skb_cb {
codel_time_t enqueue_time;
};
static struct codel_skb_cb *get_codel_cb(const struct sk_buff *skb)
{
qdisc_cb_private_validate(skb, sizeof(struct codel_skb_cb));
return (struct codel_skb_cb *)qdisc_skb_cb(skb)->data;
}
static codel_time_t codel_get_enqueue_time(const struct sk_buff *skb)
{
return get_codel_cb(skb)->enqueue_time;
}
static void codel_set_enqueue_time(struct sk_buff *skb)
{
get_codel_cb(skb)->enqueue_time = codel_get_time();
}
static inline u32 codel_time_to_us(codel_time_t val)
{
u64 valns = ((u64)val << CODEL_SHIFT);
do_div(valns, NSEC_PER_USEC);
return (u32)valns;
}
/**
* struct codel_params - contains codel parameters
* @target: target queue size (in time units)
* @interval: width of moving time window
* @ecn: is Explicit Congestion Notification enabled
*/
struct codel_params {
codel_time_t target;
codel_time_t interval;
bool ecn;
};
/**
* struct codel_vars - contains codel variables
* @count: how many drops we've done since the last time we
* entered dropping state
* @lastcount: count at entry to dropping state
* @dropping: set to true if in dropping state
* @rec_inv_sqrt: reciprocal value of sqrt(count) >> 1
* @first_above_time: when we went (or will go) continuously above target
* for interval
* @drop_next: time to drop next packet, or when we dropped last
* @ldelay: sojourn time of last dequeued packet
*/
struct codel_vars {
u32 count;
u32 lastcount;
bool dropping;
u16 rec_inv_sqrt;
codel_time_t first_above_time;
codel_time_t drop_next;
codel_time_t ldelay;
};
#define REC_INV_SQRT_BITS (8 * sizeof(u16)) /* or sizeof_in_bits(rec_inv_sqrt) */
/* needed shift to get a Q0.32 number from rec_inv_sqrt */
#define REC_INV_SQRT_SHIFT (32 - REC_INV_SQRT_BITS)
/**
* struct codel_stats - contains codel shared variables and stats
* @maxpacket: largest packet we've seen so far
* @drop_count: temp count of dropped packets in dequeue()
* ecn_mark: number of packets we ECN marked instead of dropping
*/
struct codel_stats {
u32 maxpacket;
u32 drop_count;
u32 ecn_mark;
};
static void codel_params_init(struct codel_params *params)
{
params->interval = MS2TIME(100);
params->target = MS2TIME(5);
params->ecn = false;
}
static void codel_vars_init(struct codel_vars *vars)
{
memset(vars, 0, sizeof(*vars));
}
static void codel_stats_init(struct codel_stats *stats)
{
stats->maxpacket = 256;
}
/*
* http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots
* new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
*
* Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
*/
static void codel_Newton_step(struct codel_vars *vars)
{
u32 invsqrt = ((u32)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 32;
u64 val = (3LL << 32) - ((u64)vars->count * invsqrt2);
val >>= 2; /* avoid overflow in following multiply */
val = (val * invsqrt) >> (32 - 2 + 1);
vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
}
/*
* CoDel control_law is t + interval/sqrt(count)
* We maintain in rec_inv_sqrt the reciprocal value of sqrt(count) to avoid
* both sqrt() and divide operation.
*/
static codel_time_t codel_control_law(codel_time_t t,
codel_time_t interval,
u32 rec_inv_sqrt)
{
return t + reciprocal_scale(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
}
static bool codel_should_drop(const struct sk_buff *skb,
struct Qdisc *sch,
struct codel_vars *vars,
struct codel_params *params,
struct codel_stats *stats,
codel_time_t now)
{
bool ok_to_drop;
if (!skb) {
vars->first_above_time = 0;
return false;
}
vars->ldelay = now - codel_get_enqueue_time(skb);
sch->qstats.backlog -= qdisc_pkt_len(skb);
if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))
stats->maxpacket = qdisc_pkt_len(skb);
if (codel_time_before(vars->ldelay, params->target) ||
sch->qstats.backlog <= stats->maxpacket) {
/* went below - stay below for at least interval */
vars->first_above_time = 0;
return false;
}
ok_to_drop = false;
if (vars->first_above_time == 0) {
/* just went above from below. If we stay above
* for at least interval we'll say it's ok to drop
*/
vars->first_above_time = now + params->interval;
} else if (codel_time_after(now, vars->first_above_time)) {
ok_to_drop = true;
}
return ok_to_drop;
}
typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
struct Qdisc *sch);
static struct sk_buff *codel_dequeue(struct Qdisc *sch,
struct codel_params *params,
struct codel_vars *vars,
struct codel_stats *stats,
codel_skb_dequeue_t dequeue_func)
{
struct sk_buff *skb = dequeue_func(vars, sch);
codel_time_t now;
bool drop;
if (!skb) {
vars->dropping = false;
return skb;
}
now = codel_get_time();
drop = codel_should_drop(skb, sch, vars, params, stats, now);
if (vars->dropping) {
if (!drop) {
/* sojourn time below target - leave dropping state */
vars->dropping = false;
} else if (codel_time_after_eq(now, vars->drop_next)) {
/* It's time for the next drop. Drop the current
* packet and dequeue the next. The dequeue might
* take us out of dropping state.
* If not, schedule the next drop.
* A large backlog might result in drop rates so high
* that the next drop should happen now,
* hence the while loop.
*/
while (vars->dropping &&
codel_time_after_eq(now, vars->drop_next)) {
vars->count++; /* dont care of possible wrap
* since there is no more divide
*/
codel_Newton_step(vars);
if (params->ecn && INET_ECN_set_ce(skb)) {
stats->ecn_mark++;
vars->drop_next =
codel_control_law(vars->drop_next,
params->interval,
vars->rec_inv_sqrt);
goto end;
}
qdisc_drop(skb, sch);
stats->drop_count++;
skb = dequeue_func(vars, sch);
if (!codel_should_drop(skb, sch,
vars, params, stats, now)) {
/* leave dropping state */
vars->dropping = false;
} else {
/* and schedule the next drop */
vars->drop_next =
codel_control_law(vars->drop_next,
params->interval,
vars->rec_inv_sqrt);
}
}
}
} else if (drop) {
u32 delta;
if (params->ecn && INET_ECN_set_ce(skb)) {
stats->ecn_mark++;
} else {
qdisc_drop(skb, sch);
stats->drop_count++;
skb = dequeue_func(vars, sch);
drop = codel_should_drop(skb, sch, vars, params,
stats, now);
}
vars->dropping = true;
/* if min went above target close to when we last went below it
* assume that the drop rate that controlled the queue on the
* last cycle is a good starting point to control it now.
*/
delta = vars->count - vars->lastcount;
if (delta > 1 &&
codel_time_before(now - vars->drop_next,
16 * params->interval)) {
vars->count = delta;
/* we dont care if rec_inv_sqrt approximation
* is not very precise :
* Next Newton steps will correct it quadratically.
*/
codel_Newton_step(vars);
} else {
vars->count = 1;
vars->rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
}
vars->lastcount = vars->count;
vars->drop_next = codel_control_law(now, params->interval,
vars->rec_inv_sqrt);
}
end:
return skb;
}
#endif
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