Skip to content

Commit

Permalink
net: sched: pie: export symbols to be reused by FQ-PIE
Browse files Browse the repository at this point in the history 
This patch makes the drop_early(), calculate_probability() and
pie_process_dequeue() functions generic enough to be used by
both PIE and FQ-PIE (to be added in a future commit). The major
change here is in the way the functions take in arguments. This
patch exports these functions and makes FQ-PIE dependent on
sch_pie.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
  • Loading branch information
@mohittahiliani @davem330
mohittahiliani authored and davem330 committed Jan 23, 2020
1 parent 00ea2fb commit 5205ea0
Show file tree
Hide file tree
Showing 2 changed files with 97 additions and 85 deletions.
9 changes: 9 additions & 0 deletions include/net/pie.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -124,4 +124,13 @@ static inline void pie_set_enqueue_time(struct sk_buff *skb)
get_pie_cb(skb)->enqueue_time = psched_get_time();
}

bool pie_drop_early(struct Qdisc *sch, struct pie_params *params,
struct pie_vars *vars, u32 qlen, u32 packet_size);

void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params,
struct pie_vars *vars, u32 qlen);

void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars,
u32 qlen);

#endif
173 changes: 88 additions & 85 deletions net/sched/sch_pie.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -30,64 +30,65 @@ struct pie_sched_data {
struct Qdisc *sch;
};

static bool drop_early(struct Qdisc *sch, u32 packet_size)
bool pie_drop_early(struct Qdisc *sch, struct pie_params *params,
struct pie_vars *vars, u32 qlen, u32 packet_size)
{
struct pie_sched_data *q = qdisc_priv(sch);
u64 rnd;
u64 local_prob = q->vars.prob;
u64 local_prob = 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)
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 ((q->vars.qdelay < q->params.target / 2) &&
(q->vars.prob < MAX_PROB / 5))
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,
/* If we have fewer than 2 mtu-sized packets, disable pie_drop_early,
* similar to min_th in RED
*/
if (sch->qstats.backlog < 2 * mtu)
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 (q->params.bytemode && packet_size <= mtu)
if (params->bytemode && packet_size <= mtu)
local_prob = (u64)packet_size * div_u64(local_prob, mtu);
else
local_prob = q->vars.prob;
local_prob = vars->prob;

if (local_prob == 0) {
q->vars.accu_prob = 0;
q->vars.accu_prob_overflows = 0;
vars->accu_prob = 0;
vars->accu_prob_overflows = 0;
}

if (local_prob > MAX_PROB - q->vars.accu_prob)
q->vars.accu_prob_overflows++;
if (local_prob > MAX_PROB - vars->accu_prob)
vars->accu_prob_overflows++;

q->vars.accu_prob += local_prob;
vars->accu_prob += local_prob;

if (q->vars.accu_prob_overflows == 0 &&
q->vars.accu_prob < (MAX_PROB / 100) * 85)
if (vars->accu_prob_overflows == 0 &&
vars->accu_prob < (MAX_PROB / 100) * 85)
return false;
if (q->vars.accu_prob_overflows == 8 &&
q->vars.accu_prob >= MAX_PROB / 2)
if (vars->accu_prob_overflows == 8 &&
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;
vars->accu_prob = 0;
vars->accu_prob_overflows = 0;
return true;
}

return false;
}
EXPORT_SYMBOL_GPL(pie_drop_early);

static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
Expand All @@ -100,7 +101,8 @@ static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
goto out;
}

if (!drop_early(sch, skb->len)) {
if (!pie_drop_early(sch, &q->params, &q->vars, sch->qstats.backlog,
skb->len)) {
enqueue = true;
} else if (q->params.ecn && (q->vars.prob <= MAX_PROB / 10) &&
INET_ECN_set_ce(skb)) {
Expand Down Expand Up @@ -212,26 +214,25 @@ static int pie_change(struct Qdisc *sch, struct nlattr *opt,
return 0;
}

static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb)
void pie_process_dequeue(struct sk_buff *skb, struct pie_params *params,
struct pie_vars *vars, u32 qlen)
{
struct pie_sched_data *q = qdisc_priv(sch);
int qlen = sch->qstats.backlog; /* current queue size in bytes */
psched_time_t now = psched_get_time();
u32 dtime = 0;

/* If dq_rate_estimator is disabled, calculate qdelay using the
* packet timestamp.
*/
if (!q->params.dq_rate_estimator) {
q->vars.qdelay = now - pie_get_enqueue_time(skb);
if (!params->dq_rate_estimator) {
vars->qdelay = now - pie_get_enqueue_time(skb);

if (q->vars.dq_tstamp != DTIME_INVALID)
dtime = now - q->vars.dq_tstamp;
if (vars->dq_tstamp != DTIME_INVALID)
dtime = now - vars->dq_tstamp;

q->vars.dq_tstamp = now;
vars->dq_tstamp = now;

if (qlen == 0)
q->vars.qdelay = 0;
vars->qdelay = 0;

if (dtime == 0)
return;
Expand All @@ -243,9 +244,9 @@ static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb)
* 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;
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
Expand All @@ -257,36 +258,36 @@ static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb)
* 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 (vars->dq_count != DQCOUNT_INVALID) {
vars->dq_count += skb->len;

if (q->vars.dq_count >= QUEUE_THRESHOLD) {
u32 count = q->vars.dq_count << PIE_SCALE;
if (vars->dq_count >= QUEUE_THRESHOLD) {
u32 count = vars->dq_count << PIE_SCALE;

dtime = now - q->vars.dq_tstamp;
dtime = now - vars->dq_tstamp;

if (dtime == 0)
return;

count = count / dtime;

if (q->vars.avg_dq_rate == 0)
q->vars.avg_dq_rate = count;
if (vars->avg_dq_rate == 0)
vars->avg_dq_rate = count;
else
q->vars.avg_dq_rate =
(q->vars.avg_dq_rate -
(q->vars.avg_dq_rate >> 3)) + (count >> 3);
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) {
q->vars.dq_count = DQCOUNT_INVALID;
vars->dq_count = DQCOUNT_INVALID;
} else {
q->vars.dq_count = 0;
q->vars.dq_tstamp = psched_get_time();
vars->dq_count = 0;
vars->dq_tstamp = psched_get_time();
}

goto burst_allowance_reduction;
Expand All @@ -296,18 +297,18 @@ static void pie_process_dequeue(struct Qdisc *sch, struct sk_buff *skb)
return;

burst_allowance_reduction:
if (q->vars.burst_time > 0) {
if (q->vars.burst_time > dtime)
q->vars.burst_time -= dtime;
if (vars->burst_time > 0) {
if (vars->burst_time > dtime)
vars->burst_time -= dtime;
else
q->vars.burst_time = 0;
vars->burst_time = 0;
}
}
EXPORT_SYMBOL_GPL(pie_process_dequeue);

static void calculate_probability(struct Qdisc *sch)
void pie_calculate_probability(struct pie_params *params, struct pie_vars *vars,
u32 qlen)
{
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 = 0; /* in pschedtime */
s64 delta = 0; /* determines the change in probability */
Expand All @@ -316,17 +317,17 @@ static void calculate_probability(struct Qdisc *sch)
u32 power;
bool update_prob = true;

if (q->params.dq_rate_estimator) {
qdelay_old = q->vars.qdelay;
q->vars.qdelay_old = q->vars.qdelay;
if (params->dq_rate_estimator) {
qdelay_old = vars->qdelay;
vars->qdelay_old = vars->qdelay;

if (q->vars.avg_dq_rate > 0)
qdelay = (qlen << PIE_SCALE) / q->vars.avg_dq_rate;
if (vars->avg_dq_rate > 0)
qdelay = (qlen << PIE_SCALE) / vars->avg_dq_rate;
else
qdelay = 0;
} else {
qdelay = q->vars.qdelay;
qdelay_old = q->vars.qdelay_old;
qdelay = vars->qdelay;
qdelay_old = vars->qdelay_old;
}

/* If qdelay is zero and qlen is not, it means qlen is very small,
Expand All @@ -342,18 +343,18 @@ static void calculate_probability(struct Qdisc *sch)
* 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;
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 (q->vars.prob < MAX_PROB / 10) {
if (vars->prob < MAX_PROB / 10) {
alpha >>= 1;
beta >>= 1;

power = 100;
while (q->vars.prob < div_u64(MAX_PROB, power) &&
while (vars->prob < div_u64(MAX_PROB, power) &&
power <= 1000000) {
alpha >>= 2;
beta >>= 2;
Expand All @@ -362,14 +363,14 @@ static void calculate_probability(struct Qdisc *sch)
}

/* alpha and beta should be between 0 and 32, in multiples of 1/16 */
delta += alpha * (u64)(qdelay - q->params.target);
delta += alpha * (u64)(qdelay - params->target);
delta += beta * (u64)(qdelay - qdelay_old);

oldprob = q->vars.prob;
oldprob = 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)
vars->prob >= MAX_PROB / 10)
delta = (MAX_PROB / 100) * 2;

/* Non-linear drop:
Expand All @@ -380,12 +381,12 @@ static void calculate_probability(struct Qdisc *sch)
if (qdelay > (PSCHED_NS2TICKS(250 * NSEC_PER_MSEC)))
delta += MAX_PROB / (100 / 2);

q->vars.prob += delta;
vars->prob += delta;

if (delta > 0) {
/* prevent overflow */
if (q->vars.prob < oldprob) {
q->vars.prob = MAX_PROB;
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
Expand All @@ -395,8 +396,8 @@ static void calculate_probability(struct Qdisc *sch)
}
} else {
/* prevent underflow */
if (q->vars.prob > oldprob)
q->vars.prob = 0;
if (vars->prob > oldprob)
vars->prob = 0;
}

/* Non-linear drop in probability: Reduce drop probability quickly if
Expand All @@ -405,27 +406,28 @@ static void calculate_probability(struct Qdisc *sch)

if (qdelay == 0 && qdelay_old == 0 && update_prob)
/* Reduce drop probability to 98.4% */
q->vars.prob -= q->vars.prob / 64u;
vars->prob -= vars->prob / 64;

q->vars.qdelay = qdelay;
q->vars.qlen_old = qlen;
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. If average dq_rate_estimator is enabled, 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->params.dq_rate_estimator || q->vars.avg_dq_rate > 0)) {
pie_vars_init(&q->vars);
if ((vars->qdelay < params->target / 2) &&
(vars->qdelay_old < params->target / 2) &&
vars->prob == 0 &&
(!params->dq_rate_estimator || vars->avg_dq_rate > 0)) {
pie_vars_init(vars);
}

if (!q->params.dq_rate_estimator)
q->vars.qdelay_old = qdelay;
if (!params->dq_rate_estimator)
vars->qdelay_old = qdelay;
}
EXPORT_SYMBOL_GPL(pie_calculate_probability);

static void pie_timer(struct timer_list *t)
{
Expand All @@ -434,7 +436,7 @@ 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);
pie_calculate_probability(&q->params, &q->vars, sch->qstats.backlog);

/* reset the timer to fire after 'tupdate'. tupdate is in jiffies. */
if (q->params.tupdate)
Expand Down Expand Up @@ -523,12 +525,13 @@ 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(skb, &q->params, &q->vars, sch->qstats.backlog);
return skb;
}

Expand Down

0 comments on commit 5205ea0

Please sign in to comment.