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#!/bin/bash
# debloat.sh - improves network latency by reducing excessive buffering
# and offloads on common devices and enabling fq_codel.
# Copyright 2012 M D Taht. Released into the public domain.
# This script is presently targetted to go into
# /etc/network/ifup.d on debian derived systems
# /sbin/ifup-local on rhel / centos / fedora derived systems
#
# References: http://www.bufferbloat.net/projects/codel/wiki/Best_practices_for_benchmarking_Codel_and_FQ_Codel
IFACE=$1
[[ "$IFACE" == "lo" ]] && exit 0
LL=1 # go for lowest latency
ECN=1 # enable ECN
BQLLIMIT100=3000 # at speeds below 100Mbit, 2 big packets is enough
BQLLIMIT10=1514 # at speeds below 10Mbit, 1 big packet is enough.
# Actually it would be nice to go to just one packet
QDISC=fq_codel # There are multiple variants of fq_codel in testing
FQ_LIMIT="" # the default 10000 packet limit mucks with slow start at speeds
# at 1Gbit and below. Somewhat arbitrary figures selected.
[ -z "$IFACE" ] && echo error: $0 expects IFACE parameter in environment && exit 1
ethtool=/sbin/ethtool
[ -z $ethtool ] && echo error: ethtool is required && exit 1
tc=/sbin/tc
[ -z $tc ] && echo error: tc is required && exit 1
# FIXME see if $QDISC is available. modprobe?
# BUGS - need to detect bridges.
# - Need filter to distribute across mq ethernet devices
# - needs an "undebloat" script for ifdown to restore BQL autotuning
S=/sys/class/net
FQ_OPTS=""
#FQ_OPTS="FLOWS 2048 TARGET 5ms"
[ $LL -eq 1 ] && FQ_OPTS="$FQ_OPTS quantum 500"
[ $ECN -eq 1 ] && FQ_OPTS="$FQ_OPTS ecn"
FLOW_KEYS="src,dst,proto,proto-src,proto-dst"
# For 5-tuple (flow) fairness when the same device is performing NAT
#FLOW_KEYS="nfct-src,nfct-dst,nfct-proto,nfct-proto-src,nfct-proto-dst"
# Offloads are evil in the quest for low latency
# And ethtool will abort if you attempt to turn off a
# nonexistent offload.
et() {
(
$ethtool -K $IFACE tso off
$ethtool -K $IFACE gso off
$ethtool -K $IFACE ufo off
# Presently unknown if gro/lro affect latency much
$ethtool -K $IFACE gro off
$ethtool -K $IFACE lro off
) 2> /dev/null
}
# Wifi is special in that how the queues work is pre-defined
# to be voice, video, best effort and background
wifi() {
$tc qdisc add dev $IFACE handle 1 root mq
$tc qdisc add dev $IFACE parent 1:1 $QDISC $FQ_OPTS noecn
$tc qdisc add dev $IFACE parent 1:2 $QDISC $FQ_OPTS
$tc qdisc add dev $IFACE parent 1:3 $QDISC $FQ_OPTS
$tc qdisc add dev $IFACE parent 1:4 $QDISC $FQ_OPTS noecn
}
# Hardware mq ethernet devs are special and need some sort of filter
# attached to actually use in most cases. FIXME. (see tg3)
mq() {
local I=1
$tc qdisc add dev $IFACE handle 1 root mq
for i in $S/$IFACE/queues/tx-*
do
$tc qdisc add dev $IFACE parent 1:$(printf "%x" $I) $QDISC $FQ_OPTS
I=`expr $I + 1`
done
I=`expr $I - 1`
$tc filter add dev $IFACE prio 1 protocol ip parent 1: handle 100 \
flow hash keys ${FLOW_KEYS} divisor $I baseclass 1:1
}
fq_codel() {
$tc qdisc add dev $IFACE root $QDISC $FQ_OPTS $FQ_LIMIT
}
fix_speed() {
local SPEED=`cat $S/$IFACE/speed` 2> /dev/null
if [ -n "$SPEED" ]
then
[ "$SPEED" = 4294967295 ] && echo "no ethernet speed selected. debloat estimate will be WRONG"
[ "$SPEED" -lt 1001 ] && FQ_LIMIT="limit 1200"
if [ "$SPEED" -lt 101 ]
then
[ $LL -eq 1 ] && et # for lowest latency disable offloads
BQLLIMIT=$BQLLIMIT100
FQ_LIMIT="limit 800"
[ "$SPEED" -lt 11 ] && BQLLIMIT=$BQLLIMIT10 && FQ_LIMIT="limit 400"
for I in /sys/class/net/$IFACE/queues/tx-*/byte_queue_limits/limit_max
do
echo $BQLLIMIT > $I
done
fi
fi
}
fix_queues() {
local QUEUES=`ls -d $S/$IFACE/queues/tx-* | wc -l | awk '{print $1}'`
if [ $QUEUES -gt 1 ]
then
if [ -x $S/$IFACE/phy80211 ]
then
wifi
else
mq
fi
else
fq_codel
fi
}
$tc qdisc del dev $IFACE root 2> /dev/null
fix_speed
fix_queues
/sbin/ip link set $IFACE txqueuelen 100
exit 0
|
