* [PATCH 1/2] codel: generalize the implementation
2016-04-22 12:15 [PATCH 0/2] codel: make it reuseable beyond qdiscs Michal Kazior
@ 2016-04-22 12:15 ` Michal Kazior
2016-04-22 12:15 ` [PATCH 2/2] codel: split into multiple files Michal Kazior
2016-04-25 20:45 ` [PATCH 0/2] codel: make it reuseable beyond qdiscs David Miller
2 siblings, 0 replies; 4+ messages in thread
From: Michal Kazior @ 2016-04-22 12:15 UTC (permalink / raw)
To: netdev; +Cc: davem, johannes, Michal Kazior
This strips out qdisc specific bits from the code
and makes it slightly more reusable. Codel will be
used by wireless/mac80211 in the future.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
---
include/net/codel.h | 64 +++++++++++++++++++++++++++++-------------------
net/sched/sch_codel.c | 20 ++++++++++++---
net/sched/sch_fq_codel.c | 19 +++++++++++---
3 files changed, 71 insertions(+), 32 deletions(-)
diff --git a/include/net/codel.h b/include/net/codel.h
index d168aca115cc..06ac687b4909 100644
--- a/include/net/codel.h
+++ b/include/net/codel.h
@@ -176,12 +176,10 @@ struct codel_stats {
#define CODEL_DISABLED_THRESHOLD INT_MAX
-static void codel_params_init(struct codel_params *params,
- const struct Qdisc *sch)
+static void codel_params_init(struct codel_params *params)
{
params->interval = MS2TIME(100);
params->target = MS2TIME(5);
- params->mtu = psched_mtu(qdisc_dev(sch));
params->ce_threshold = CODEL_DISABLED_THRESHOLD;
params->ecn = false;
}
@@ -226,28 +224,38 @@ static codel_time_t codel_control_law(codel_time_t t,
return t + reciprocal_scale(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
}
+typedef u32 (*codel_skb_len_t)(const struct sk_buff *skb);
+typedef codel_time_t (*codel_skb_time_t)(const struct sk_buff *skb);
+typedef void (*codel_skb_drop_t)(struct sk_buff *skb, void *ctx);
+typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
+ void *ctx);
+
static bool codel_should_drop(const struct sk_buff *skb,
- struct Qdisc *sch,
+ void *ctx,
struct codel_vars *vars,
struct codel_params *params,
struct codel_stats *stats,
+ codel_skb_len_t skb_len_func,
+ codel_skb_time_t skb_time_func,
+ u32 *backlog,
codel_time_t now)
{
bool ok_to_drop;
+ u32 skb_len;
if (!skb) {
vars->first_above_time = 0;
return false;
}
- vars->ldelay = now - codel_get_enqueue_time(skb);
- sch->qstats.backlog -= qdisc_pkt_len(skb);
+ skb_len = skb_len_func(skb);
+ vars->ldelay = now - skb_time_func(skb);
- if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))
- stats->maxpacket = qdisc_pkt_len(skb);
+ if (unlikely(skb_len > stats->maxpacket))
+ stats->maxpacket = skb_len;
if (codel_time_before(vars->ldelay, params->target) ||
- sch->qstats.backlog <= params->mtu) {
+ *backlog <= params->mtu) {
/* went below - stay below for at least interval */
vars->first_above_time = 0;
return false;
@@ -264,16 +272,17 @@ static bool codel_should_drop(const struct sk_buff *skb,
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,
+static struct sk_buff *codel_dequeue(void *ctx,
+ u32 *backlog,
struct codel_params *params,
struct codel_vars *vars,
struct codel_stats *stats,
+ codel_skb_len_t skb_len_func,
+ codel_skb_time_t skb_time_func,
+ codel_skb_drop_t drop_func,
codel_skb_dequeue_t dequeue_func)
{
- struct sk_buff *skb = dequeue_func(vars, sch);
+ struct sk_buff *skb = dequeue_func(vars, ctx);
codel_time_t now;
bool drop;
@@ -282,7 +291,8 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
return skb;
}
now = codel_get_time();
- drop = codel_should_drop(skb, sch, vars, params, stats, now);
+ drop = codel_should_drop(skb, ctx, vars, params, stats,
+ skb_len_func, skb_time_func, backlog, now);
if (vars->dropping) {
if (!drop) {
/* sojourn time below target - leave dropping state */
@@ -310,12 +320,15 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
vars->rec_inv_sqrt);
goto end;
}
- stats->drop_len += qdisc_pkt_len(skb);
- qdisc_drop(skb, sch);
+ stats->drop_len += skb_len_func(skb);
+ drop_func(skb, ctx);
stats->drop_count++;
- skb = dequeue_func(vars, sch);
- if (!codel_should_drop(skb, sch,
- vars, params, stats, now)) {
+ skb = dequeue_func(vars, ctx);
+ if (!codel_should_drop(skb, ctx,
+ vars, params, stats,
+ skb_len_func,
+ skb_time_func,
+ backlog, now)) {
/* leave dropping state */
vars->dropping = false;
} else {
@@ -333,13 +346,14 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
if (params->ecn && INET_ECN_set_ce(skb)) {
stats->ecn_mark++;
} else {
- stats->drop_len += qdisc_pkt_len(skb);
- qdisc_drop(skb, sch);
+ stats->drop_len += skb_len_func(skb);
+ drop_func(skb, ctx);
stats->drop_count++;
- skb = dequeue_func(vars, sch);
- drop = codel_should_drop(skb, sch, vars, params,
- stats, now);
+ skb = dequeue_func(vars, ctx);
+ drop = codel_should_drop(skb, ctx, vars, params,
+ stats, skb_len_func,
+ skb_time_func, backlog, now);
}
vars->dropping = true;
/* if min went above target close to when we last went below it
diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
index 9b7e2980ee5c..512a94abe351 100644
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -64,20 +64,33 @@ struct codel_sched_data {
* to dequeue a packet from queue. Note: backlog is handled in
* codel, we dont need to reduce it here.
*/
-static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
+static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
{
+ struct Qdisc *sch = ctx;
struct sk_buff *skb = __skb_dequeue(&sch->q);
+ if (skb)
+ sch->qstats.backlog -= qdisc_pkt_len(skb);
+
prefetch(&skb->end); /* we'll need skb_shinfo() */
return skb;
}
+static void drop_func(struct sk_buff *skb, void *ctx)
+{
+ struct Qdisc *sch = ctx;
+
+ qdisc_drop(skb, sch);
+}
+
static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
{
struct codel_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb;
- skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats, dequeue);
+ skb = codel_dequeue(sch, &sch->qstats.backlog, &q->params, &q->vars,
+ &q->stats, qdisc_pkt_len, codel_get_enqueue_time,
+ drop_func, dequeue_func);
/* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
* or HTB crashes. Defer it for next round.
@@ -173,9 +186,10 @@ static int codel_init(struct Qdisc *sch, struct nlattr *opt)
sch->limit = DEFAULT_CODEL_LIMIT;
- codel_params_init(&q->params, sch);
+ codel_params_init(&q->params);
codel_vars_init(&q->vars);
codel_stats_init(&q->stats);
+ q->params.mtu = psched_mtu(qdisc_dev(sch));
if (opt) {
int err = codel_change(sch, opt);
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index d3fc8f9dd3d4..dcf7266e6901 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -220,8 +220,9 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
* to dequeue a packet from queue. Note: backlog is handled in
* codel, we dont need to reduce it here.
*/
-static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
+static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
{
+ struct Qdisc *sch = ctx;
struct fq_codel_sched_data *q = qdisc_priv(sch);
struct fq_codel_flow *flow;
struct sk_buff *skb = NULL;
@@ -231,10 +232,18 @@ static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
skb = dequeue_head(flow);
q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
sch->q.qlen--;
+ sch->qstats.backlog -= qdisc_pkt_len(skb);
}
return skb;
}
+static void drop_func(struct sk_buff *skb, void *ctx)
+{
+ struct Qdisc *sch = ctx;
+
+ qdisc_drop(skb, sch);
+}
+
static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
{
struct fq_codel_sched_data *q = qdisc_priv(sch);
@@ -263,8 +272,9 @@ begin:
prev_ecn_mark = q->cstats.ecn_mark;
prev_backlog = sch->qstats.backlog;
- skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
- dequeue);
+ skb = codel_dequeue(sch, &sch->qstats.backlog, &q->cparams,
+ &flow->cvars, &q->cstats, qdisc_pkt_len,
+ codel_get_enqueue_time, drop_func, dequeue_func);
flow->dropped += q->cstats.drop_count - prev_drop_count;
flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
@@ -423,9 +433,10 @@ static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
q->perturbation = prandom_u32();
INIT_LIST_HEAD(&q->new_flows);
INIT_LIST_HEAD(&q->old_flows);
- codel_params_init(&q->cparams, sch);
+ codel_params_init(&q->cparams);
codel_stats_init(&q->cstats);
q->cparams.ecn = true;
+ q->cparams.mtu = psched_mtu(qdisc_dev(sch));
if (opt) {
int err = fq_codel_change(sch, opt);
--
2.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH 2/2] codel: split into multiple files
2016-04-22 12:15 [PATCH 0/2] codel: make it reuseable beyond qdiscs Michal Kazior
2016-04-22 12:15 ` [PATCH 1/2] codel: generalize the implementation Michal Kazior
@ 2016-04-22 12:15 ` Michal Kazior
2016-04-25 20:45 ` [PATCH 0/2] codel: make it reuseable beyond qdiscs David Miller
2 siblings, 0 replies; 4+ messages in thread
From: Michal Kazior @ 2016-04-22 12:15 UTC (permalink / raw)
To: netdev; +Cc: davem, johannes, Michal Kazior
It was impossible to include codel.h for the
purpose of having access to codel_params or
codel_vars structure definitions and using them
for embedding in other more complex structures.
This splits allows codel.h itself to be treated
like any other header file while codel_qdisc.h and
codel_impl.h contain function definitions with
logic that was previously in codel.h.
This copies over copyrights and doesn't involve
code changes other than adding a few additional
include directives to net/sched/sch*codel.c.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
---
include/net/codel.h | 223 ----------------------------------------
include/net/codel_impl.h | 255 ++++++++++++++++++++++++++++++++++++++++++++++
include/net/codel_qdisc.h | 73 +++++++++++++
net/sched/sch_codel.c | 2 +
net/sched/sch_fq_codel.c | 2 +
5 files changed, 332 insertions(+), 223 deletions(-)
create mode 100644 include/net/codel_impl.h
create mode 100644 include/net/codel_qdisc.h
diff --git a/include/net/codel.h b/include/net/codel.h
index 06ac687b4909..a6e428f80135 100644
--- a/include/net/codel.h
+++ b/include/net/codel.h
@@ -87,27 +87,6 @@ static inline codel_time_t codel_get_time(void)
((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);
@@ -176,212 +155,10 @@ struct codel_stats {
#define CODEL_DISABLED_THRESHOLD INT_MAX
-static void codel_params_init(struct codel_params *params)
-{
- params->interval = MS2TIME(100);
- params->target = MS2TIME(5);
- params->ce_threshold = CODEL_DISABLED_THRESHOLD;
- 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 = 0;
-}
-
-/*
- * 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);
-}
-
typedef u32 (*codel_skb_len_t)(const struct sk_buff *skb);
typedef codel_time_t (*codel_skb_time_t)(const struct sk_buff *skb);
typedef void (*codel_skb_drop_t)(struct sk_buff *skb, void *ctx);
typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
void *ctx);
-static bool codel_should_drop(const struct sk_buff *skb,
- void *ctx,
- struct codel_vars *vars,
- struct codel_params *params,
- struct codel_stats *stats,
- codel_skb_len_t skb_len_func,
- codel_skb_time_t skb_time_func,
- u32 *backlog,
- codel_time_t now)
-{
- bool ok_to_drop;
- u32 skb_len;
-
- if (!skb) {
- vars->first_above_time = 0;
- return false;
- }
-
- skb_len = skb_len_func(skb);
- vars->ldelay = now - skb_time_func(skb);
-
- if (unlikely(skb_len > stats->maxpacket))
- stats->maxpacket = skb_len;
-
- if (codel_time_before(vars->ldelay, params->target) ||
- *backlog <= params->mtu) {
- /* 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;
-}
-
-static struct sk_buff *codel_dequeue(void *ctx,
- u32 *backlog,
- struct codel_params *params,
- struct codel_vars *vars,
- struct codel_stats *stats,
- codel_skb_len_t skb_len_func,
- codel_skb_time_t skb_time_func,
- codel_skb_drop_t drop_func,
- codel_skb_dequeue_t dequeue_func)
-{
- struct sk_buff *skb = dequeue_func(vars, ctx);
- codel_time_t now;
- bool drop;
-
- if (!skb) {
- vars->dropping = false;
- return skb;
- }
- now = codel_get_time();
- drop = codel_should_drop(skb, ctx, vars, params, stats,
- skb_len_func, skb_time_func, backlog, 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;
- }
- stats->drop_len += skb_len_func(skb);
- drop_func(skb, ctx);
- stats->drop_count++;
- skb = dequeue_func(vars, ctx);
- if (!codel_should_drop(skb, ctx,
- vars, params, stats,
- skb_len_func,
- skb_time_func,
- backlog, 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 {
- stats->drop_len += skb_len_func(skb);
- drop_func(skb, ctx);
- stats->drop_count++;
-
- skb = dequeue_func(vars, ctx);
- drop = codel_should_drop(skb, ctx, vars, params,
- stats, skb_len_func,
- skb_time_func, backlog, 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:
- if (skb && codel_time_after(vars->ldelay, params->ce_threshold) &&
- INET_ECN_set_ce(skb))
- stats->ce_mark++;
- return skb;
-}
#endif
diff --git a/include/net/codel_impl.h b/include/net/codel_impl.h
new file mode 100644
index 000000000000..d289b91dcd65
--- /dev/null
+++ b/include/net/codel_impl.h
@@ -0,0 +1,255 @@
+#ifndef __NET_SCHED_CODEL_IMPL_H
+#define __NET_SCHED_CODEL_IMPL_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) 2012,2015 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.
+ *
+ */
+
+/* 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
+ */
+
+static void codel_params_init(struct codel_params *params)
+{
+ params->interval = MS2TIME(100);
+ params->target = MS2TIME(5);
+ params->ce_threshold = CODEL_DISABLED_THRESHOLD;
+ 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 = 0;
+}
+
+/*
+ * 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,
+ void *ctx,
+ struct codel_vars *vars,
+ struct codel_params *params,
+ struct codel_stats *stats,
+ codel_skb_len_t skb_len_func,
+ codel_skb_time_t skb_time_func,
+ u32 *backlog,
+ codel_time_t now)
+{
+ bool ok_to_drop;
+ u32 skb_len;
+
+ if (!skb) {
+ vars->first_above_time = 0;
+ return false;
+ }
+
+ skb_len = skb_len_func(skb);
+ vars->ldelay = now - skb_time_func(skb);
+
+ if (unlikely(skb_len > stats->maxpacket))
+ stats->maxpacket = skb_len;
+
+ if (codel_time_before(vars->ldelay, params->target) ||
+ *backlog <= params->mtu) {
+ /* 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;
+}
+
+static struct sk_buff *codel_dequeue(void *ctx,
+ u32 *backlog,
+ struct codel_params *params,
+ struct codel_vars *vars,
+ struct codel_stats *stats,
+ codel_skb_len_t skb_len_func,
+ codel_skb_time_t skb_time_func,
+ codel_skb_drop_t drop_func,
+ codel_skb_dequeue_t dequeue_func)
+{
+ struct sk_buff *skb = dequeue_func(vars, ctx);
+ codel_time_t now;
+ bool drop;
+
+ if (!skb) {
+ vars->dropping = false;
+ return skb;
+ }
+ now = codel_get_time();
+ drop = codel_should_drop(skb, ctx, vars, params, stats,
+ skb_len_func, skb_time_func, backlog, 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;
+ }
+ stats->drop_len += skb_len_func(skb);
+ drop_func(skb, ctx);
+ stats->drop_count++;
+ skb = dequeue_func(vars, ctx);
+ if (!codel_should_drop(skb, ctx,
+ vars, params, stats,
+ skb_len_func,
+ skb_time_func,
+ backlog, 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 {
+ stats->drop_len += skb_len_func(skb);
+ drop_func(skb, ctx);
+ stats->drop_count++;
+
+ skb = dequeue_func(vars, ctx);
+ drop = codel_should_drop(skb, ctx, vars, params,
+ stats, skb_len_func,
+ skb_time_func, backlog, 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:
+ if (skb && codel_time_after(vars->ldelay, params->ce_threshold) &&
+ INET_ECN_set_ce(skb))
+ stats->ce_mark++;
+ return skb;
+}
+
+#endif
diff --git a/include/net/codel_qdisc.h b/include/net/codel_qdisc.h
new file mode 100644
index 000000000000..8144d9cd2908
--- /dev/null
+++ b/include/net/codel_qdisc.h
@@ -0,0 +1,73 @@
+#ifndef __NET_SCHED_CODEL_QDISC_H
+#define __NET_SCHED_CODEL_QDISC_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) 2012,2015 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.
+ *
+ */
+
+/* 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
+ */
+
+/* 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();
+}
+
+#endif
diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
index 512a94abe351..dddf3bb65a32 100644
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -49,6 +49,8 @@
#include <linux/prefetch.h>
#include <net/pkt_sched.h>
#include <net/codel.h>
+#include <net/codel_impl.h>
+#include <net/codel_qdisc.h>
#define DEFAULT_CODEL_LIMIT 1000
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index dcf7266e6901..a5e420b3d4ab 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -24,6 +24,8 @@
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/codel.h>
+#include <net/codel_impl.h>
+#include <net/codel_qdisc.h>
/* Fair Queue CoDel.
*
--
2.1.4
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