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Message-Id: <20190331174005.5841-2-gautamramk@gmail.com>
Date: Sun, 31 Mar 2019 23:10:04 +0530
From: Gautam Ramakrishnan <gautamramk@...il.com>
To: jhs@...atatu.com
Cc: davem@...emloft.net, netdev@...r.kernel.org,
Gautam Ramakrishnan <gautamramk@...il.com>,
"Mohit P . Tahiliani" <tahiliani@...k.edu.in>,
"Sachin D . Patil" <sdp.sachin@...il.com>,
Mohit Bhasi <mohitbhasi1998@...il.com>,
"V . Saicharan" <vsaicharan1998@...il.com>,
Leslie Monis <lesliemonis@...il.com>,
Dave Taht <dave.taht@...il.com>
Subject: [RFC net-next 1/2] net: sched: pie: refactor PIE
From: Mohit P. Tahiliani <tahiliani@...k.edu.in>
This patch refactors the code for the PIE qdisc. It breaks
sch_pie.c down into 'sch_pie.c' and 'pie.h'. This enables
the addition of qdiscs such as FQ-PIE that make use of the
components of PIE.
Signed-off-by: Mohit P. Tahiliani <tahiliani@...k.edu.in>
Signed-off-by: Sachin D. Patil <sdp.sachin@...il.com>
Signed-off-by: Mohit Bhasi <mohitbhasi1998@...il.com>
Signed-off-by: V. Saicharan <vsaicharan1998@...il.com>
Signed-off-by: Leslie Monis <lesliemonis@...il.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@...il.com>
Cc: Dave Taht <dave.taht@...il.com>
---
include/net/pie.h | 330 ++++++++++++++++++++++++++++++++++++++++++++
net/sched/sch_pie.c | 314 +----------------------------------------
2 files changed, 336 insertions(+), 308 deletions(-)
create mode 100644 include/net/pie.h
diff --git a/include/net/pie.h b/include/net/pie.h
new file mode 100644
index 000000000000..1cc295f468b4
--- /dev/null
+++ b/include/net/pie.h
@@ -0,0 +1,330 @@
+/*
+ * include/net/pie.h Proportional Integral Controller Enhanced
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * Original Author: Vijay Subramanian <vijaynsu@...co.com>
+ * Original Author: Mythili Prabhu <mysuryan@...co.com>
+ *
+ * ECN support is added by Naeem Khademi <naeemk@....uio.no>
+ * University of Oslo, Norway.
+ *
+ * References:
+ * RFC 8033: https://tools.ietf.org/html/rfc8033
+ */
+
+#ifndef __NET_SCHED_PIE_H
+#define __NET_SCHED_PIE_H
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/skbuff.h>
+#include <net/pkt_sched.h>
+#include <net/inet_ecn.h>
+
+#define QUEUE_THRESHOLD 16384
+#define DQCOUNT_INVALID -1
+#define MAX_PROB 0xffffffffffffffff
+#define PIE_SCALE 8
+
+/* parameters used */
+struct pie_params {
+ psched_time_t target; /* user specified target delay in pschedtime */
+ u32 tupdate; /* timer frequency (in jiffies) */
+ u32 limit; /* number of packets that can be enqueued */
+ u32 alpha; /* alpha and beta are between 0 and 32 */
+ u32 beta; /* and are used for shift relative to 1 */
+ bool ecn; /* true if ecn is enabled */
+ bool bytemode; /* to scale drop early prob based on pkt size */
+};
+
+/* variables used */
+struct pie_vars {
+ u64 prob; /* probability but scaled by u64 limit. */
+ psched_time_t burst_time;
+ psched_time_t qdelay;
+ psched_time_t qdelay_old;
+ u64 dq_count; /* measured in bytes */
+ psched_time_t dq_tstamp; /* drain rate */
+ u64 accu_prob; /* accumulated drop probability */
+ u32 avg_dq_rate; /* bytes per pschedtime tick,scaled */
+ u32 qlen_old; /* in bytes */
+ u8 accu_prob_overflows; /* overflows of accu_prob */
+};
+
+/* statistics gathering */
+struct pie_stats {
+ u32 packets_in; /* total number of packets enqueued */
+ u32 dropped; /* packets dropped due to pie_action */
+ u32 overlimit; /* dropped due to lack of space in queue */
+ u32 maxq; /* maximum queue size */
+ u32 ecn_mark; /* packets marked with ECN */
+};
+
+static void pie_params_init(struct pie_params *params)
+{
+ params->alpha = 2;
+ params->beta = 20;
+ params->tupdate = usecs_to_jiffies(15 * USEC_PER_MSEC); /* 15 ms */
+ params->limit = 1000; /* default of 1000 packets */
+ params->target = PSCHED_NS2TICKS(15 * NSEC_PER_MSEC); /* 15 ms */
+ params->ecn = false;
+ params->bytemode = false;
+}
+
+static void pie_vars_init(struct pie_vars *vars)
+{
+ vars->dq_count = DQCOUNT_INVALID;
+ vars->accu_prob = 0;
+ vars->avg_dq_rate = 0;
+ /* default of 150 ms in pschedtime */
+ vars->burst_time = PSCHED_NS2TICKS(150 * NSEC_PER_MSEC);
+ vars->accu_prob_overflows = 0;
+}
+
+static bool drop_early(struct Qdisc *sch, u32 qlen, u32 packet_size,
+ struct pie_vars *vars, struct pie_params *params)
+{
+ u64 rnd;
+ u64 local_prob = vars->prob;
+ u32 mtu = psched_mtu(qdisc_dev(sch));
+
+ /* If there is still burst allowance left skip random early drop */
+ if (vars->burst_time > 0)
+ return false;
+
+ /* If current delay is less than half of target, and
+ * if drop prob is low already, disable early_drop
+ */
+ if ((vars->qdelay < params->target / 2) &&
+ (vars->prob < MAX_PROB / 5))
+ return false;
+
+ /* If we have fewer than 2 mtu-sized packets, disable drop_early,
+ * similar to min_th in RED
+ */
+ if (qlen < 2 * mtu)
+ return false;
+
+ /* If bytemode is turned on, use packet size to compute new
+ * probablity. Smaller packets will have lower drop prob in this case
+ */
+ if (params->bytemode && packet_size <= mtu)
+ local_prob = (u64)packet_size * div_u64(local_prob, mtu);
+ else
+ local_prob = vars->prob;
+
+ if (local_prob == 0) {
+ vars->accu_prob = 0;
+ vars->accu_prob_overflows = 0;
+ }
+
+ if (local_prob > MAX_PROB - vars->accu_prob)
+ vars->accu_prob_overflows++;
+
+ vars->accu_prob += local_prob;
+
+ if (vars->accu_prob_overflows == 0 &&
+ vars->accu_prob < (MAX_PROB / 100) * 85)
+ return false;
+ if (vars->accu_prob_overflows == 8 &&
+ vars->accu_prob >= MAX_PROB / 2)
+ return true;
+
+ prandom_bytes(&rnd, 8);
+ if (rnd < local_prob) {
+ vars->accu_prob = 0;
+ vars->accu_prob_overflows = 0;
+ return true;
+ }
+
+ return false;
+}
+
+static void pie_process_dequeue(u32 qlen, struct sk_buff *skb,
+ struct pie_vars *vars)
+{
+ /* If current queue is about 10 packets or more and dq_count is unset
+ * we have enough packets to calculate the drain rate. Save
+ * current time as dq_tstamp and start measurement cycle.
+ */
+ if (qlen >= QUEUE_THRESHOLD && vars->dq_count == DQCOUNT_INVALID) {
+ vars->dq_tstamp = psched_get_time();
+ vars->dq_count = 0;
+ }
+
+ /* Calculate the average drain rate from this value. If queue length
+ * has receded to a small value viz., <= QUEUE_THRESHOLD bytes,reset
+ * the dq_count to -1 as we don't have enough packets to calculate the
+ * drain rate anymore The following if block is entered only when we
+ * have a substantial queue built up (QUEUE_THRESHOLD bytes or more)
+ * and we calculate the drain rate for the threshold here. dq_count is
+ * in bytes, time difference in psched_time, hence rate is in
+ * bytes/psched_time.
+ */
+ if (vars->dq_count != DQCOUNT_INVALID) {
+ vars->dq_count += skb->len;
+
+ if (vars->dq_count >= QUEUE_THRESHOLD) {
+ psched_time_t now = psched_get_time();
+ u32 dtime = now - vars->dq_tstamp;
+ u32 count = vars->dq_count << PIE_SCALE;
+
+ if (dtime == 0)
+ return;
+
+ count = count / dtime;
+
+ if (vars->avg_dq_rate == 0)
+ vars->avg_dq_rate = count;
+ else
+ vars->avg_dq_rate =
+ (vars->avg_dq_rate -
+ (vars->avg_dq_rate >> 3)) + (count >> 3);
+
+ /* If the queue has receded below the threshold, we hold
+ * on to the last drain rate calculated, else we reset
+ * dq_count to 0 to re-enter the if block when the next
+ * packet is dequeued
+ */
+ if (qlen < QUEUE_THRESHOLD) {
+ vars->dq_count = DQCOUNT_INVALID;
+ } else {
+ vars->dq_count = 0;
+ vars->dq_tstamp = psched_get_time();
+ }
+
+ if (vars->burst_time > 0) {
+ if (vars->burst_time > dtime)
+ vars->burst_time -= dtime;
+ else
+ vars->burst_time = 0;
+ }
+ }
+ }
+}
+
+static void calculate_probability(u32 qlen, struct pie_vars *vars,
+ struct pie_params *params)
+{
+ psched_time_t qdelay = 0; /* in pschedtime */
+ psched_time_t qdelay_old = vars->qdelay; /* in pschedtime */
+ s64 delta = 0; /* determines the change in probability */
+ u64 oldprob;
+ u64 alpha, beta;
+ u32 power;
+ bool update_prob = true;
+
+ vars->qdelay_old = vars->qdelay;
+
+ if (vars->avg_dq_rate > 0)
+ qdelay = (qlen << PIE_SCALE) / vars->avg_dq_rate;
+ else
+ qdelay = 0;
+
+ /* If qdelay is zero and qlen is not, it means qlen is very small, less
+ * than dequeue_rate, so we do not update probabilty in this round
+ */
+ if (qdelay == 0 && qlen != 0)
+ update_prob = false;
+
+ /* In the algorithm, alpha and beta are between 0 and 2 with typical
+ * value for alpha as 0.125. In this implementation, we use values 0-32
+ * passed from user space to represent this. Also, alpha and beta have
+ * unit of HZ and need to be scaled before they can used to update
+ * probability. alpha/beta are updated locally below by scaling down
+ * by 16 to come to 0-2 range.
+ */
+ alpha = ((u64)params->alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+ beta = ((u64)params->beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
+
+ /* We scale alpha and beta differently depending on how heavy the
+ * congestion is. Please see RFC 8033 for details.
+ */
+ if (vars->prob < MAX_PROB / 10) {
+ alpha >>= 1;
+ beta >>= 1;
+
+ power = 100;
+ while (vars->prob < div_u64(MAX_PROB, power) &&
+ power <= 1000000) {
+ alpha >>= 2;
+ beta >>= 2;
+ power *= 10;
+ }
+ }
+
+ /* alpha and beta should be between 0 and 32, in multiples of 1/16 */
+ delta += alpha * (u64)(qdelay - params->target);
+ delta += beta * (u64)(qdelay - qdelay_old);
+
+ oldprob = vars->prob;
+
+ /* to ensure we increase probability in steps of no more than 2% */
+ if (delta > (s64)(MAX_PROB / (100 / 2)) &&
+ vars->prob >= MAX_PROB / 10)
+ delta = (MAX_PROB / 100) * 2;
+
+ /* Non-linear drop:
+ * Tune drop probability to increase quickly for high delays(>= 250ms)
+ * 250ms is derived through experiments and provides error protection
+ */
+
+ if (qdelay > (PSCHED_NS2TICKS(250 * NSEC_PER_MSEC)))
+ delta += MAX_PROB / (100 / 2);
+
+ vars->prob += delta;
+
+ if (delta > 0) {
+ /* prevent overflow */
+ if (vars->prob < oldprob) {
+ vars->prob = MAX_PROB;
+ /* Prevent normalization error. If probability is at
+ * maximum value already, we normalize it here, and
+ * skip the check to do a non-linear drop in the next
+ * section.
+ */
+ update_prob = false;
+ }
+ } else {
+ /* prevent underflow */
+ if (vars->prob > oldprob)
+ vars->prob = 0;
+ }
+
+ /* Non-linear drop in probability: Reduce drop probability quickly if
+ * delay is 0 for 2 consecutive Tupdate periods.
+ */
+
+ if (qdelay == 0 && qdelay_old == 0 && update_prob)
+ /* Reduce drop probability to 98.4% */
+ vars->prob -= vars->prob / 64u;
+
+ vars->qdelay = qdelay;
+ vars->qlen_old = qlen;
+
+ /* We restart the measurement cycle if the following conditions are met
+ * 1. If the delay has been low for 2 consecutive Tupdate periods
+ * 2. Calculated drop probability is zero
+ * 3. We have atleast one estimate for the avg_dq_rate ie.,
+ * is a non-zero value
+ */
+ if ((vars->qdelay < params->target / 2) &&
+ (vars->qdelay_old < params->target / 2) &&
+ vars->prob == 0 &&
+ vars->avg_dq_rate > 0)
+ pie_vars_init(vars);
+}
+
+#endif /* __NET_SCHED_PIE_H */
diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
index 1cc0c7b74aa3..f81a8c145914 100644
--- a/net/sched/sch_pie.c
+++ b/net/sched/sch_pie.c
@@ -20,53 +20,7 @@
* RFC 8033: https://tools.ietf.org/html/rfc8033
*/
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/types.h>
-#include <linux/kernel.h>
-#include <linux/errno.h>
-#include <linux/skbuff.h>
-#include <net/pkt_sched.h>
-#include <net/inet_ecn.h>
-
-#define QUEUE_THRESHOLD 16384
-#define DQCOUNT_INVALID -1
-#define MAX_PROB 0xffffffffffffffff
-#define PIE_SCALE 8
-
-/* parameters used */
-struct pie_params {
- psched_time_t target; /* user specified target delay in pschedtime */
- u32 tupdate; /* timer frequency (in jiffies) */
- u32 limit; /* number of packets that can be enqueued */
- u32 alpha; /* alpha and beta are between 0 and 32 */
- u32 beta; /* and are used for shift relative to 1 */
- bool ecn; /* true if ecn is enabled */
- bool bytemode; /* to scale drop early prob based on pkt size */
-};
-
-/* variables used */
-struct pie_vars {
- u64 prob; /* probability but scaled by u64 limit. */
- psched_time_t burst_time;
- psched_time_t qdelay;
- psched_time_t qdelay_old;
- u64 dq_count; /* measured in bytes */
- psched_time_t dq_tstamp; /* drain rate */
- u64 accu_prob; /* accumulated drop probability */
- u32 avg_dq_rate; /* bytes per pschedtime tick,scaled */
- u32 qlen_old; /* in bytes */
- u8 accu_prob_overflows; /* overflows of accu_prob */
-};
-
-/* statistics gathering */
-struct pie_stats {
- u32 packets_in; /* total number of packets enqueued */
- u32 dropped; /* packets dropped due to pie_action */
- u32 overlimit; /* dropped due to lack of space in queue */
- u32 maxq; /* maximum queue size */
- u32 ecn_mark; /* packets marked with ECN */
-};
+#include <net/pie.h>
/* private data for the Qdisc */
struct pie_sched_data {
@@ -77,86 +31,6 @@ struct pie_sched_data {
struct Qdisc *sch;
};
-static void pie_params_init(struct pie_params *params)
-{
- params->alpha = 2;
- params->beta = 20;
- params->tupdate = usecs_to_jiffies(15 * USEC_PER_MSEC); /* 15 ms */
- params->limit = 1000; /* default of 1000 packets */
- params->target = PSCHED_NS2TICKS(15 * NSEC_PER_MSEC); /* 15 ms */
- params->ecn = false;
- params->bytemode = false;
-}
-
-static void pie_vars_init(struct pie_vars *vars)
-{
- vars->dq_count = DQCOUNT_INVALID;
- vars->accu_prob = 0;
- vars->avg_dq_rate = 0;
- /* default of 150 ms in pschedtime */
- vars->burst_time = PSCHED_NS2TICKS(150 * NSEC_PER_MSEC);
- vars->accu_prob_overflows = 0;
-}
-
-static bool drop_early(struct Qdisc *sch, u32 packet_size)
-{
- struct pie_sched_data *q = qdisc_priv(sch);
- u64 rnd;
- u64 local_prob = q->vars.prob;
- u32 mtu = psched_mtu(qdisc_dev(sch));
-
- /* If there is still burst allowance left skip random early drop */
- if (q->vars.burst_time > 0)
- return false;
-
- /* If current delay is less than half of target, and
- * if drop prob is low already, disable early_drop
- */
- if ((q->vars.qdelay < q->params.target / 2) &&
- (q->vars.prob < MAX_PROB / 5))
- return false;
-
- /* If we have fewer than 2 mtu-sized packets, disable drop_early,
- * similar to min_th in RED
- */
- if (sch->qstats.backlog < 2 * mtu)
- return false;
-
- /* If bytemode is turned on, use packet size to compute new
- * probablity. Smaller packets will have lower drop prob in this case
- */
- if (q->params.bytemode && packet_size <= mtu)
- local_prob = (u64)packet_size * div_u64(local_prob, mtu);
- else
- local_prob = q->vars.prob;
-
- if (local_prob == 0) {
- q->vars.accu_prob = 0;
- q->vars.accu_prob_overflows = 0;
- }
-
- if (local_prob > MAX_PROB - q->vars.accu_prob)
- q->vars.accu_prob_overflows++;
-
- q->vars.accu_prob += local_prob;
-
- if (q->vars.accu_prob_overflows == 0 &&
- q->vars.accu_prob < (MAX_PROB / 100) * 85)
- return false;
- if (q->vars.accu_prob_overflows == 8 &&
- q->vars.accu_prob >= MAX_PROB / 2)
- return true;
-
- prandom_bytes(&rnd, 8);
- if (rnd < local_prob) {
- q->vars.accu_prob = 0;
- q->vars.accu_prob_overflows = 0;
- return true;
- }
-
- return false;
-}
-
static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
@@ -168,7 +42,8 @@ static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
goto out;
}
- if (!drop_early(sch, skb->len)) {
+ if (!drop_early(sch, sch->qstats.backlog, skb->len, &q->vars,
+ &q->params)) {
enqueue = true;
} else if (q->params.ecn && (q->vars.prob <= MAX_PROB / 10) &&
INET_ECN_set_ce(skb)) {
@@ -270,184 +145,6 @@ static int pie_change(struct Qdisc *sch, struct nlattr *opt,
return 0;
}
-static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb)
-{
- struct pie_sched_data *q = qdisc_priv(sch);
- int qlen = sch->qstats.backlog; /* current queue size in bytes */
-
- /* If current queue is about 10 packets or more and dq_count is unset
- * we have enough packets to calculate the drain rate. Save
- * current time as dq_tstamp and start measurement cycle.
- */
- if (qlen >= QUEUE_THRESHOLD && q->vars.dq_count == DQCOUNT_INVALID) {
- q->vars.dq_tstamp = psched_get_time();
- q->vars.dq_count = 0;
- }
-
- /* Calculate the average drain rate from this value. If queue length
- * has receded to a small value viz., <= QUEUE_THRESHOLD bytes,reset
- * the dq_count to -1 as we don't have enough packets to calculate the
- * drain rate anymore The following if block is entered only when we
- * have a substantial queue built up (QUEUE_THRESHOLD bytes or more)
- * and we calculate the drain rate for the threshold here. dq_count is
- * in bytes, time difference in psched_time, hence rate is in
- * bytes/psched_time.
- */
- if (q->vars.dq_count != DQCOUNT_INVALID) {
- q->vars.dq_count += skb->len;
-
- if (q->vars.dq_count >= QUEUE_THRESHOLD) {
- psched_time_t now = psched_get_time();
- u32 dtime = now - q->vars.dq_tstamp;
- u32 count = q->vars.dq_count << PIE_SCALE;
-
- if (dtime == 0)
- return;
-
- count = count / dtime;
-
- if (q->vars.avg_dq_rate == 0)
- q->vars.avg_dq_rate = count;
- else
- q->vars.avg_dq_rate =
- (q->vars.avg_dq_rate -
- (q->vars.avg_dq_rate >> 3)) + (count >> 3);
-
- /* If the queue has receded below the threshold, we hold
- * on to the last drain rate calculated, else we reset
- * dq_count to 0 to re-enter the if block when the next
- * packet is dequeued
- */
- if (qlen < QUEUE_THRESHOLD) {
- q->vars.dq_count = DQCOUNT_INVALID;
- } else {
- q->vars.dq_count = 0;
- q->vars.dq_tstamp = psched_get_time();
- }
-
- if (q->vars.burst_time > 0) {
- if (q->vars.burst_time > dtime)
- q->vars.burst_time -= dtime;
- else
- q->vars.burst_time = 0;
- }
- }
- }
-}
-
-static void calculate_probability(struct Qdisc *sch)
-{
- struct pie_sched_data *q = qdisc_priv(sch);
- u32 qlen = sch->qstats.backlog; /* queue size in bytes */
- psched_time_t qdelay = 0; /* in pschedtime */
- psched_time_t qdelay_old = q->vars.qdelay; /* in pschedtime */
- s64 delta = 0; /* determines the change in probability */
- u64 oldprob;
- u64 alpha, beta;
- u32 power;
- bool update_prob = true;
-
- q->vars.qdelay_old = q->vars.qdelay;
-
- if (q->vars.avg_dq_rate > 0)
- qdelay = (qlen << PIE_SCALE) / q->vars.avg_dq_rate;
- else
- qdelay = 0;
-
- /* If qdelay is zero and qlen is not, it means qlen is very small, less
- * than dequeue_rate, so we do not update probabilty in this round
- */
- if (qdelay == 0 && qlen != 0)
- update_prob = false;
-
- /* In the algorithm, alpha and beta are between 0 and 2 with typical
- * value for alpha as 0.125. In this implementation, we use values 0-32
- * passed from user space to represent this. Also, alpha and beta have
- * unit of HZ and need to be scaled before they can used to update
- * probability. alpha/beta are updated locally below by scaling down
- * by 16 to come to 0-2 range.
- */
- alpha = ((u64)q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
- beta = ((u64)q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
-
- /* We scale alpha and beta differently depending on how heavy the
- * congestion is. Please see RFC 8033 for details.
- */
- if (q->vars.prob < MAX_PROB / 10) {
- alpha >>= 1;
- beta >>= 1;
-
- power = 100;
- while (q->vars.prob < div_u64(MAX_PROB, power) &&
- power <= 1000000) {
- alpha >>= 2;
- beta >>= 2;
- power *= 10;
- }
- }
-
- /* alpha and beta should be between 0 and 32, in multiples of 1/16 */
- delta += alpha * (u64)(qdelay - q->params.target);
- delta += beta * (u64)(qdelay - qdelay_old);
-
- oldprob = q->vars.prob;
-
- /* to ensure we increase probability in steps of no more than 2% */
- if (delta > (s64)(MAX_PROB / (100 / 2)) &&
- q->vars.prob >= MAX_PROB / 10)
- delta = (MAX_PROB / 100) * 2;
-
- /* Non-linear drop:
- * Tune drop probability to increase quickly for high delays(>= 250ms)
- * 250ms is derived through experiments and provides error protection
- */
-
- if (qdelay > (PSCHED_NS2TICKS(250 * NSEC_PER_MSEC)))
- delta += MAX_PROB / (100 / 2);
-
- q->vars.prob += delta;
-
- if (delta > 0) {
- /* prevent overflow */
- if (q->vars.prob < oldprob) {
- q->vars.prob = MAX_PROB;
- /* Prevent normalization error. If probability is at
- * maximum value already, we normalize it here, and
- * skip the check to do a non-linear drop in the next
- * section.
- */
- update_prob = false;
- }
- } else {
- /* prevent underflow */
- if (q->vars.prob > oldprob)
- q->vars.prob = 0;
- }
-
- /* Non-linear drop in probability: Reduce drop probability quickly if
- * delay is 0 for 2 consecutive Tupdate periods.
- */
-
- if (qdelay == 0 && qdelay_old == 0 && update_prob)
- /* Reduce drop probability to 98.4% */
- q->vars.prob -= q->vars.prob / 64u;
-
- q->vars.qdelay = qdelay;
- q->vars.qlen_old = qlen;
-
- /* We restart the measurement cycle if the following conditions are met
- * 1. If the delay has been low for 2 consecutive Tupdate periods
- * 2. Calculated drop probability is zero
- * 3. We have atleast one estimate for the avg_dq_rate ie.,
- * is a non-zero value
- */
- if ((q->vars.qdelay < q->params.target / 2) &&
- (q->vars.qdelay_old < q->params.target / 2) &&
- q->vars.prob == 0 &&
- q->vars.avg_dq_rate > 0)
- pie_vars_init(&q->vars);
-}
-
static void pie_timer(struct timer_list *t)
{
struct pie_sched_data *q = from_timer(q, t, adapt_timer);
@@ -455,7 +152,7 @@ static void pie_timer(struct timer_list *t)
spinlock_t *root_lock = qdisc_lock(qdisc_root_sleeping(sch));
spin_lock(root_lock);
- calculate_probability(sch);
+ calculate_probability(sch->qstats.backlog, &q->vars, &q->params);
/* reset the timer to fire after 'tupdate'. tupdate is in jiffies. */
if (q->params.tupdate)
@@ -537,12 +234,13 @@ static int pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
static struct sk_buff *pie_qdisc_dequeue(struct Qdisc *sch)
{
+ struct pie_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb = qdisc_dequeue_head(sch);
if (!skb)
return NULL;
- pie_process_dequeue(sch, skb);
+ pie_process_dequeue(sch->qstats.backlog, skb, &q->vars);
return skb;
}
--
2.17.1
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