forked from luck/tmp_suning_uos_patched
net: sched: pie: add more cases to auto-tune alpha and beta
The current implementation scales the local alpha and beta variables in the calculate_probability function by the same amount for all values of drop probability below 1%. RFC 8033 suggests using additional cases for auto-tuning alpha and beta when the drop probability is less than 1%. In order to add more auto-tuning cases, MAX_PROB must be scaled by u64 instead of u32 to prevent underflow when scaling the local alpha and beta variables in the calculate_probability function. Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in> Signed-off-by: Dhaval Khandla <dhavaljkhandla26@gmail.com> Signed-off-by: Hrishikesh Hiraskar <hrishihiraskar@gmail.com> Signed-off-by: Manish Kumar B <bmanish15597@gmail.com> Signed-off-by: Sachin D. Patil <sdp.sachin@gmail.com> Signed-off-by: Leslie Monis <lesliemonis@gmail.com> Acked-by: Dave Taht <dave.taht@gmail.com> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -954,7 +954,7 @@ enum {
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#define TCA_PIE_MAX (__TCA_PIE_MAX - 1)
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struct tc_pie_xstats {
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__u32 prob; /* current probability */
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__u64 prob; /* current probability */
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__u32 delay; /* current delay in ms */
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__u32 avg_dq_rate; /* current average dq_rate in bits/pie_time */
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__u32 packets_in; /* total number of packets enqueued */
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@ -33,7 +33,7 @@
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#define QUEUE_THRESHOLD 16384
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#define DQCOUNT_INVALID -1
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#define MAX_PROB 0xffffffff
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#define MAX_PROB 0xffffffffffffffff
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#define PIE_SCALE 8
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/* parameters used */
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@ -49,7 +49,7 @@ struct pie_params {
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/* variables used */
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struct pie_vars {
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u32 prob; /* probability but scaled by u32 limit. */
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u64 prob; /* probability but scaled by u64 limit. */
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psched_time_t burst_time;
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psched_time_t qdelay;
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psched_time_t qdelay_old;
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@ -99,8 +99,8 @@ static void pie_vars_init(struct pie_vars *vars)
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static bool drop_early(struct Qdisc *sch, u32 packet_size)
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{
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struct pie_sched_data *q = qdisc_priv(sch);
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u32 rnd;
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u32 local_prob = q->vars.prob;
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u64 rnd;
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u64 local_prob = q->vars.prob;
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u32 mtu = psched_mtu(qdisc_dev(sch));
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/* If there is still burst allowance left skip random early drop */
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@ -124,11 +124,11 @@ static bool drop_early(struct Qdisc *sch, u32 packet_size)
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* probablity. Smaller packets will have lower drop prob in this case
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*/
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if (q->params.bytemode && packet_size <= mtu)
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local_prob = (local_prob / mtu) * packet_size;
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local_prob = (u64)packet_size * div_u64(local_prob, mtu);
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else
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local_prob = q->vars.prob;
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rnd = prandom_u32();
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prandom_bytes(&rnd, 8);
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if (rnd < local_prob)
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return true;
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@ -317,9 +317,10 @@ static void calculate_probability(struct Qdisc *sch)
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u32 qlen = sch->qstats.backlog; /* queue size in bytes */
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psched_time_t qdelay = 0; /* in pschedtime */
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psched_time_t qdelay_old = q->vars.qdelay; /* in pschedtime */
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s32 delta = 0; /* determines the change in probability */
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u32 oldprob;
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u32 alpha, beta;
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s64 delta = 0; /* determines the change in probability */
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u64 oldprob;
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u64 alpha, beta;
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u32 power;
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bool update_prob = true;
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q->vars.qdelay_old = q->vars.qdelay;
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@ -339,38 +340,36 @@ static void calculate_probability(struct Qdisc *sch)
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* value for alpha as 0.125. In this implementation, we use values 0-32
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* passed from user space to represent this. Also, alpha and beta have
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* unit of HZ and need to be scaled before they can used to update
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* probability. alpha/beta are updated locally below by 1) scaling them
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* appropriately 2) scaling down by 16 to come to 0-2 range.
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* Please see paper for details.
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*
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* We scale alpha and beta differently depending on whether we are in
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* light, medium or high dropping mode.
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* probability. alpha/beta are updated locally below by scaling down
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* by 16 to come to 0-2 range.
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*/
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if (q->vars.prob < MAX_PROB / 100) {
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alpha =
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(q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 7;
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beta =
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(q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 7;
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} else if (q->vars.prob < MAX_PROB / 10) {
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alpha =
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(q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 5;
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beta =
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(q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 5;
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} else {
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alpha =
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(q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
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beta =
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(q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
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alpha = ((u64)q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
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beta = ((u64)q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 4;
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/* We scale alpha and beta differently depending on how heavy the
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* congestion is. Please see RFC 8033 for details.
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*/
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if (q->vars.prob < MAX_PROB / 10) {
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alpha >>= 1;
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beta >>= 1;
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power = 100;
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while (q->vars.prob < div_u64(MAX_PROB, power) &&
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power <= 1000000) {
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alpha >>= 2;
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beta >>= 2;
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power *= 10;
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}
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}
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/* alpha and beta should be between 0 and 32, in multiples of 1/16 */
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delta += alpha * ((qdelay - q->params.target));
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delta += beta * ((qdelay - qdelay_old));
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delta += alpha * (u64)(qdelay - q->params.target);
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delta += beta * (u64)(qdelay - qdelay_old);
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oldprob = q->vars.prob;
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/* to ensure we increase probability in steps of no more than 2% */
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if (delta > (s32)(MAX_PROB / (100 / 2)) &&
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if (delta > (s64)(MAX_PROB / (100 / 2)) &&
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q->vars.prob >= MAX_PROB / 10)
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delta = (MAX_PROB / 100) * 2;
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