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Fix the queue delay estimation in PIE/FQ-PIE when the timestamp

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(TS) method is used.  When packet timestamp is used, the "current_qdelay"
keeps storing the last queue delay value calculated in the dequeue
function.  Therefore, when a burst of packets arrives followed by
a pause, the "current_qdelay" will store a high value caused by the
burst and stick to that value during the pause because the queue
delay measurement is done inside the dequeue function.  This causes
the drop probability calculation function to calculate high drop
probability value instead of zero and prevents the burst allowance
mechanism from working properly.  Fix this problem by resetting
"current_qdelay" inside the drop probability calculation function
when the queue length is zero and TS option is used.

Submitted by:	Rasool Al-Saadi <ralsaadi@swin.edu.au>
MFC after:	1 week
This commit is contained in:
truckman 2017-05-19 08:38:03 +00:00
parent e77dc5266b
commit 5cd4f2ce44
2 changed files with 16 additions and 6 deletions
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11
sys/netpfil/ipfw/dn_aqm_pie.c
View File

@ -211,11 +211,16 @@ calculate_drop_prob(void *x)
pprms = pst->parms;
prob = pst->drop_prob;
/* calculate current qdelay */
if (pprms->flags & PIE_DEPRATEEST_ENABLED) {
/* calculate current qdelay using DRE method.
* If TS is used and no data in the queue, reset current_qdelay
* as it stays at last value during dequeue process.
*/
if (pprms->flags & PIE_DEPRATEEST_ENABLED)
pst->current_qdelay = ((uint64_t)pst->pq->ni.len_bytes *
pst->avg_dq_time) >> PIE_DQ_THRESHOLD_BITS;
}
else
if (!pst->pq->ni.len_bytes)
pst->current_qdelay = 0;
/* calculate drop probability */
p = (int64_t)pprms->alpha *

11
sys/netpfil/ipfw/dn_sched_fq_pie.c
View File

@ -383,11 +383,16 @@ fq_calculate_drop_prob(void *x)
pprms = pst->parms;
prob = pst->drop_prob;
/* calculate current qdelay */
if (pprms->flags & PIE_DEPRATEEST_ENABLED) {
/* calculate current qdelay using DRE method.
* If TS is used and no data in the queue, reset current_qdelay
* as it stays at last value during dequeue process.
*/
if (pprms->flags & PIE_DEPRATEEST_ENABLED)
pst->current_qdelay = ((uint64_t)q->stats.len_bytes * pst->avg_dq_time)
>> PIE_DQ_THRESHOLD_BITS;
}
else
if (!q->stats.len_bytes)
pst->current_qdelay = 0;
/* calculate drop probability */
p = (int64_t)pprms->alpha *