Skip to content

Commit

Permalink
selftests: mlxsw: Add a test for UC behavior under MC flood
Browse files Browse the repository at this point in the history 
A so-called "MC-aware" mode has recently been enabled in mlxsw. In
MC-aware mode, BUM traffic is handled in a special way so that when a
switch is flooded with BUM, UC performance isn't unduly impacted.
Without enablement of this mode, a stream of BUM traffic can cause
sustained UC throughput drop in excess of 99 %.

Add a test for this behavior. Compare how much UC throughput degrades as
a stream of broadcast frames floods the switch. A minimal degradation is
tolerated to cover for glitches in traffic injection performance.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
  • Loading branch information
Petr Machata authored and David S. Miller committed Sep 20, 2018
1 parent a381ed1 commit b5638d4
Showing 1 changed file with 347 additions and 0 deletions.
347 changes: 347 additions & 0 deletions tools/testing/selftests/drivers/net/mlxsw/qos_mc_aware.sh
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,347 @@
#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
#
# A test for switch behavior under MC overload. An issue in Spectrum chips
# causes throughput of UC traffic to drop severely when a switch is under heavy
# MC load. This issue can be overcome by putting the switch to MC-aware mode.
# This test verifies that UC performance stays intact even as the switch is
# under MC flood, and therefore that the MC-aware mode is enabled and correctly
# configured.
#
# Because mlxsw throttles CPU port, the traffic can't actually reach userspace
# at full speed. That makes it impossible to use iperf3 to simply measure the
# throughput, because many packets (that reach $h3) don't get to the kernel at
# all even in UDP mode (the situation is even worse in TCP mode, where one can't
# hope to see more than a couple Mbps).
#
# So instead we send traffic with mausezahn and use RX ethtool counters at $h3.
# Multicast traffic is untagged, unicast traffic is tagged with PCP 1. Therefore
# each gets a different priority and we can use per-prio ethtool counters to
# measure the throughput. In order to avoid prioritizing unicast traffic, prio
# qdisc is installed on $swp3 and maps all priorities to the same band #7 (and
# thus TC 0).
#
# Mausezahn can't actually saturate the links unless it's using large frames.
# Thus we set MTU to 10K on all involved interfaces. Then both unicast and
# multicast traffic uses 8K frames.
#
# +-----------------------+ +----------------------------------+
# | H1 | | H2 |
# | | | unicast --> + $h2.111 |
# | | | traffic | 192.0.2.129/28 |
# | multicast | | | e-qos-map 0:1 |
# | traffic | | | |
# | $h1 + <----- | | + $h2 |
# +-----|-----------------+ +--------------|-------------------+
# | |
# +-----|-------------------------------------------------|-------------------+
# | + $swp1 + $swp2 |
# | | >1Gbps | >1Gbps |
# | +---|----------------+ +----------|----------------+ |
# | | + $swp1.1 | | + $swp2.111 | |
# | | BR1 | SW | BR111 | |
# | | + $swp3.1 | | + $swp3.111 | |
# | +---|----------------+ +----------|----------------+ |
# | \_________________________________________________/ |
# | | |
# | + $swp3 |
# | | 1Gbps bottleneck |
# | | prio qdisc: {0..7} -> 7 |
# +------------------------------------|--------------------------------------+
# |
# +--|-----------------+
# | + $h3 H3 |
# | | |
# | + $h3.111 |
# | 192.0.2.130/28 |
# +--------------------+

ALL_TESTS="
ping_ipv4
test_mc_aware
"

lib_dir=$(dirname $0)/../../../net/forwarding

NUM_NETIFS=6
source $lib_dir/lib.sh

h1_create()
{
simple_if_init $h1
mtu_set $h1 10000
}

h1_destroy()
{
mtu_restore $h1
simple_if_fini $h1
}

h2_create()
{
simple_if_init $h2
mtu_set $h2 10000

vlan_create $h2 111 v$h2 192.0.2.129/28
ip link set dev $h2.111 type vlan egress-qos-map 0:1
}

h2_destroy()
{
vlan_destroy $h2 111

mtu_restore $h2
simple_if_fini $h2
}

h3_create()
{
simple_if_init $h3
mtu_set $h3 10000

vlan_create $h3 111 v$h3 192.0.2.130/28
}

h3_destroy()
{
vlan_destroy $h3 111

mtu_restore $h3
simple_if_fini $h3
}

switch_create()
{
ip link set dev $swp1 up
mtu_set $swp1 10000

ip link set dev $swp2 up
mtu_set $swp2 10000

ip link set dev $swp3 up
mtu_set $swp3 10000

vlan_create $swp2 111
vlan_create $swp3 111

ethtool -s $swp3 speed 1000 autoneg off
tc qdisc replace dev $swp3 root handle 3: \
prio bands 8 priomap 7 7 7 7 7 7 7 7

ip link add name br1 type bridge vlan_filtering 0
ip link set dev br1 up
ip link set dev $swp1 master br1
ip link set dev $swp3 master br1

ip link add name br111 type bridge vlan_filtering 0
ip link set dev br111 up
ip link set dev $swp2.111 master br111
ip link set dev $swp3.111 master br111
}

switch_destroy()
{
ip link del dev br111
ip link del dev br1

tc qdisc del dev $swp3 root handle 3:
ethtool -s $swp3 autoneg on

vlan_destroy $swp3 111
vlan_destroy $swp2 111

mtu_restore $swp3
ip link set dev $swp3 down

mtu_restore $swp2
ip link set dev $swp2 down

mtu_restore $swp1
ip link set dev $swp1 down
}

setup_prepare()
{
h1=${NETIFS[p1]}
swp1=${NETIFS[p2]}

swp2=${NETIFS[p3]}
h2=${NETIFS[p4]}

swp3=${NETIFS[p5]}
h3=${NETIFS[p6]}

h3mac=$(mac_get $h3)

vrf_prepare

h1_create
h2_create
h3_create
switch_create
}

cleanup()
{
pre_cleanup

switch_destroy
h3_destroy
h2_destroy
h1_destroy

vrf_cleanup
}

ping_ipv4()
{
ping_test $h2 192.0.2.130
}

humanize()
{
local speed=$1; shift

for unit in bps Kbps Mbps Gbps; do
if (($(echo "$speed < 1024" | bc))); then
break
fi

speed=$(echo "scale=1; $speed / 1024" | bc)
done

echo "$speed${unit}"
}

rate()
{
local t0=$1; shift
local t1=$1; shift
local interval=$1; shift

echo $((8 * (t1 - t0) / interval))
}

check_rate()
{
local rate=$1; shift
local min=$1; shift
local what=$1; shift

if ((rate > min)); then
return 0
fi

echo "$what $(humanize $ir) < $(humanize $min_ingress)" > /dev/stderr
return 1
}

measure_uc_rate()
{
local what=$1; shift

local interval=10
local i
local ret=0

# Dips in performance might cause momentary ingress rate to drop below
# 1Gbps. That wouldn't saturate egress and MC would thus get through,
# seemingly winning bandwidth on account of UC. Demand at least 2Gbps
# average ingress rate to somewhat mitigate this.
local min_ingress=2147483648

mausezahn $h2.111 -p 8000 -A 192.0.2.129 -B 192.0.2.130 -c 0 \
-a own -b $h3mac -t udp -q &
sleep 1

for i in {5..0}; do
local t0=$(ethtool_stats_get $h3 rx_octets_prio_1)
local u0=$(ethtool_stats_get $swp2 rx_octets_prio_1)
sleep $interval
local t1=$(ethtool_stats_get $h3 rx_octets_prio_1)
local u1=$(ethtool_stats_get $swp2 rx_octets_prio_1)

local ir=$(rate $u0 $u1 $interval)
local er=$(rate $t0 $t1 $interval)

if check_rate $ir $min_ingress "$what ingress rate"; then
break
fi

# Fail the test if we can't get the throughput.
if ((i == 0)); then
ret=1
fi
done

# Suppress noise from killing mausezahn.
{ kill %% && wait; } 2>/dev/null

echo $ir $er
exit $ret
}

test_mc_aware()
{
RET=0

local -a uc_rate
uc_rate=($(measure_uc_rate "UC-only"))
check_err $? "Could not get high enough UC-only ingress rate"
local ucth1=${uc_rate[1]}

mausezahn $h1 -p 8000 -c 0 -a own -b bc -t udp -q &

local d0=$(date +%s)
local t0=$(ethtool_stats_get $h3 rx_octets_prio_0)
local u0=$(ethtool_stats_get $swp1 rx_octets_prio_0)

local -a uc_rate_2
uc_rate_2=($(measure_uc_rate "UC+MC"))
check_err $? "Could not get high enough UC+MC ingress rate"
local ucth2=${uc_rate_2[1]}

local d1=$(date +%s)
local t1=$(ethtool_stats_get $h3 rx_octets_prio_0)
local u1=$(ethtool_stats_get $swp1 rx_octets_prio_0)

local deg=$(bc <<< "
scale=2
ret = 100 * ($ucth1 - $ucth2) / $ucth1
if (ret > 0) { ret } else { 0 }
")
check_err $(bc <<< "$deg > 10")

local interval=$((d1 - d0))
local mc_ir=$(rate $u0 $u1 $interval)
local mc_er=$(rate $t0 $t1 $interval)

# Suppress noise from killing mausezahn.
{ kill %% && wait; } 2>/dev/null

log_test "UC performace under MC overload"

echo "UC-only throughput $(humanize $ucth1)"
echo "UC+MC throughput $(humanize $ucth2)"
echo "Degradation $deg %"
echo
echo "Full report:"
echo " UC only:"
echo " ingress UC throughput $(humanize ${uc_rate[0]})"
echo " egress UC throughput $(humanize ${uc_rate[1]})"
echo " UC+MC:"
echo " ingress UC throughput $(humanize ${uc_rate_2[0]})"
echo " egress UC throughput $(humanize ${uc_rate_2[1]})"
echo " ingress MC throughput $(humanize $mc_ir)"
echo " egress MC throughput $(humanize $mc_er)"
}

trap cleanup EXIT

setup_prepare
setup_wait

tests_run

exit $EXIT_STATUS

0 comments on commit b5638d4

Please sign in to comment.