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net: sched: pie: avoid slow division in drop probability decay

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As per RFC 8033, it is sufficient for the drop probability
decay factor to have a value of (1 - 1/64) instead of 98%.
This avoids the need to do slow division.

Suggested-by: David Laight <David.Laight@aculab.com>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Leslie Monis 2019-02-28 18:06:54 +05:30 committed by David S. Miller
parent 4a8acef78e
commit 6c97da1415
1 changed files with 2 additions and 1 deletions
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3
net/sched/sch_pie.c
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@ -429,7 +429,8 @@ static void calculate_probability(struct Qdisc *sch)
*/
if (qdelay == 0 && qdelay_old == 0 && update_prob)
q->vars.prob = 98 * div_u64(q->vars.prob, 100);
/* Reduce drop probability to 98.4% */
q->vars.prob -= q->vars.prob / 64u;
q->vars.qdelay = qdelay;
q->vars.qlen_old = qlen;