qos-scripts update:

- rewrite the RED qdisc calculations and add some comments
this should fix the warnings about bursting (should also fix quirks with various linespeed settings)
- reduce the calculated overhead for upstream, while i'm at it...


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@7782 3c298f89-4303-0410-b956-a3cf2f4a3e73

1 files changed, 30 insertions, 9 deletions

diff --git a/package/qos-scripts/files/usr/lib/qos/tcrules.awk b/package/qos-scripts/files/usr/lib/qos/tcrules.awk
index d236b2df93..7bef85b0d0 100644
--- a/package/qos-scripts/files/usr/lib/qos/tcrules.awk
+++ b/package/qos-scripts/files/usr/lib/qos/tcrules.awk
@@ -77,20 +77,41 @@ END {
 	# leaf qdisc
 	avpkt = 1200
 	for (i = 1; i <= n; i++) {
-		ql = int((avgrate[i] + linespeed) * 1024 / (8 * pktsize[i]))
 		printf "tc qdisc add dev "device" parent 1:"class[i]"0 handle "class[i]"00: "
+
+		# RED parameters - also used to determine the queue length for sfq
+		# calculate min value. for links <= 256 kbit, we use 1500 bytes
+		# use 50 ms queue length as min threshold for faster links
+		# max threshold is fixed to 3*min
+		base_pkt=3000
+		base_rate=256
+		min_lat=50
+		if (maxrate[i] <= base_rate) min = base_pkt
+		else min = int(maxrate[i] * 1024 / 8 * 0.05)
+		max = 3 * min
+		limit = (min + max) * 3
+
 		if (rtm1[i] > 0) {
 			# rt class - use sfq
-			print "sfq perturb 2 limit " ql
+			print "sfq perturb 2 limit "  limit
 		} else {
-			# non-rt class - use red
-			min = int(maxrate[i] * 1024 / 8 * 0.05)
-			if (min < avpkt) min = avpkt
-			dqb = 8 * min;
-			max = int(2.1*min)
-			rburst = int((2*min + max) / (3 * avpkt))
+			# non-rt class - use RED
+
+			avpkt = pktsize[i]
+			# don't use avpkt values less than 500 bytes
+			if (avpkt < 500) avpkt = 500
+			# if avpkt is too close to min, scale down avpkt to allow proper bursting
+			if (avpkt > min * 0.70) avpkt *= 0.70
+
+
+			# according to http://www.cs.unc.edu/~jeffay/papers/IEEE-ToN-01.pdf a drop
+			# probability somewhere between 0.1 and 0.2 should be a good tradeoff
+			# between link utilization and response time (0.1: response; 0.2: utilization)
+			prob="0.12"
+		
+			rburst=int((2*min + max) / (3 * avpkt))
 			if (rburst < 2) rburst = 2
-			print "red min " min " max " max " burst " rburst " avpkt " avpkt " limit " dqb " probability 0.04 ecn"
+			print "red min " min " max " max " burst " rburst " avpkt " avpkt " limit " limit " probability " prob " ecn"
 		}
 	}