Move RED parameter computation to common code

Useful for WRED and shaper RED class.

2 files changed, 33 insertions, 13 deletions

diff --git a/lib/Vyatta/Qos/ShaperClass.pm b/lib/Vyatta/Qos/ShaperClass.pm
index 4d95f42..5e1db8d 100644
--- a/lib/Vyatta/Qos/ShaperClass.pm
+++ b/lib/Vyatta/Qos/ShaperClass.pm
@@ -158,24 +158,19 @@ sub fifoQdisc {
 #   burst        := (2 * min + max) / (3 * average)
 sub redQdisc {
     my ( $self, $dev, $rate ) = @_;
+    my $avg = 1000;
+    my ($qmin, $qmax, $burst) = RedParam($rate, 500, $avg);
+
     my $limit = $self->{_limit};
-    my $avg   = 1000;
     my $qlimit;
-
-    if ( defined $limit ) {
-        $qlimit = $limit * $avg;    # red limit in bytes
-    }
-    else {
-
-        # rate is in bits/sec so queue-limit = 8 * 500ms * rate
-        $qlimit = $rate / 2;
+    if ($limit) {
+	$qlimit = $limit * $avg;
+    } else {
+	$qlimit = 4 * $qmax;
     }
-    my $qmax = $qlimit / 8;
-    my $qmin = $qmax / 3;
 
     printf "red limit %d min %d max %d avpkt %d", $qlimit, $qmin, $qmax, $avg;
-    printf " burst %d probability 0.02 bandwidth %d ecn\n",
-      ( 2 * $qmin + $qmax ) / ( 3 * $avg ), $rate / 1000;
+    printf " burst %d probability 0.02 bandwidth %d ecn\n", $burst, $rate / 1000;
 }
 
 my %qdiscOptions = (
@@ -185,6 +180,12 @@ my %qdiscOptions = (
     'drop-tail'     => \&fifoQdisc,
 );
 
+sub get_rate {
+    my ($self, $speed) = @_;
+
+    return _getPercentRate( $self->{_rate}, $speed );
+}
+
 sub gen_class {
     my ( $self, $dev, $qdisc, $parent, $speed ) = @_;
     my $rate = _getPercentRate( $self->{_rate},    $speed );
diff --git a/lib/Vyatta/Qos/Util.pm b/lib/Vyatta/Qos/Util.pm
index 3aefbd8..72b4963 100644
--- a/lib/Vyatta/Qos/Util.pm
+++ b/lib/Vyatta/Qos/Util.pm
@@ -319,4 +319,23 @@ sub ethtoolRate {
     return $rate;
 }
 
+# Compute parameters for RED algorithim based on bandwidth and latency
+#
+#                        0.01 * Bandwidth Share * Desired Latency * Network Bandwidth
+# Maximum Threshold = -------------------------------------------------------------------
+#                                    8 bits/byte* 1000 ms/sec
+#
+# Minimum Threshold = 1/2 * Maximum Threshold
+# Avpkt = Average Packet Length
+# Burst = ( 2 * MinThreshold + MaxThreshold) / ( 3 * Avpkt )
+# Limit = 4 * MaxThreshold
+sub RedParam {
+    my ($bandwidth, $latency, $avgpkt) = @_;
+    my $qmax = ($bandwidth * $latency) / 8000;
+    my $qmin = $qmax / 2;
+    my $burst = ( 2 * $qmin + $qmax ) / ( 3 * $avgpkt );
+
+    return ($qmin, $qmax, $burst);
+}
+
 1;