Commit 6c97da14 authored Feb 28, 2019 by Leslie Monis Committed by David S. Miller Feb 28, 2019

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



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>

parent 4a8acef7

net/sched/sch_pie.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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;