[Cake] cake and hfsc rate limiters outperforming htb on one-armed router

[Pete Heist <pete@heistp.net>]

For whatever reason, I’m seeing the rate limiters in cake and hfsc vastly outperform htb in the one-armed router configuration I described in my previous thread. To simplify things, I apply the qdiscs with a single class only at egress of eth0 on apu1a:

apu2a   <— default VLAN —>   apu1a   <— VLAN 3300 —>   apu2b

I use iperf3 from apu2a to apu2b and find the rate at which things break down. Whereas cake and hfsc can both reach around 850mbit, htb is breaking down at around 200mbit, which seems rather strange. This could be a function of the older kernel I have to use, the hardware, or maybe htb just isn’t suited well to this task for some reason. I wish I knew, as I’d rather be using htb for this task than hfsc (especially given the lockup issue with cake)...

——

#!/bin/bash 

# point where iperf3 throughput drops below ~93% of theoretical:
# htb: 200mbit
# hfsc: 850mbit
# cake: 850mbit

IFACE=eth0
RATE=850mbit

start_htb() {
        stop
        tc qdisc add dev $IFACE root handle 1: htb default 1
        tc class add dev $IFACE parent 1: classid 1:1 htb rate $RATE ceil $RATE
        tc qdisc add dev $IFACE parent 1:1 handle 10: fq_codel
}

start_hfsc() {
        stop
        tc qdisc add dev $IFACE root handle 1: hfsc default 1
        tc class add dev $IFACE parent 1: classid 1:1 hfsc sc rate $RATE ul rate $RATE
        tc qdisc add dev $IFACE parent 1:1 handle 10: fq_codel
}

start_cake() {
        stop
        tc qdisc add dev $IFACE root cake bandwidth $RATE
}

stop() {
        tc qdisc del dev $IFACE root &>/dev/null
        tc qdisc del dev $IFACE ingress &>/dev/null
}

"$@“
——

root@apu1a:~/rate_limiters# uname -a
Linux apu1a 3.16.7-ckt9-voyage #1 SMP Thu Apr 23 11:10:44 HKT 2015 i686 GNU/Linux

root@apu1a:~/rate_limiters# cat /proc/cpuinfo 
processor	: 0
vendor_id	: AuthenticAMD
cpu family	: 20
model		: 2
model name	: AMD G-T40E Processor
stepping	: 0
microcode	: 0x5000101
cpu MHz		: 800.000
cache size	: 512 KB
physical id	: 0
siblings	: 2
core id		: 0
cpu cores	: 2
apicid		: 0
initial apicid	: 0
fdiv_bug	: no
f00f_bug	: no
coma_bug	: no
fpu		: yes
fpu_exception	: yes
cpuid level	: 6
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc nonstop_tsc extd_apicid aperfmperf pni monitor ssse3 cx16 popcnt lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch ibs skinit wdt arat hw_pstate npt lbrv svm_lock nrip_save pausefilter vmmcall
bogomips	: 1999.83
clflush size	: 64
cache_alignment	: 64
address sizes	: 36 bits physical, 48 bits virtual
power management: ts ttp tm stc 100mhzsteps hwpstate

processor	: 1
vendor_id	: AuthenticAMD
cpu family	: 20
model		: 2
model name	: AMD G-T40E Processor
stepping	: 0
microcode	: 0x5000101
cpu MHz		: 800.000
cache size	: 512 KB
physical id	: 0
siblings	: 2
core id		: 1
cpu cores	: 2
apicid		: 1
initial apicid	: 1
fdiv_bug	: no
f00f_bug	: no
coma_bug	: no
fpu		: yes
fpu_exception	: yes
cpuid level	: 6
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc nonstop_tsc extd_apicid aperfmperf pni monitor ssse3 cx16 popcnt lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch ibs skinit wdt arat hw_pstate npt lbrv svm_lock nrip_save pausefilter vmmcall
bogomips	: 1999.83
clflush size	: 64
cache_alignment	: 64
address sizes	: 36 bits physical, 48 bits virtual
power management: ts ttp tm stc 100mhzsteps hwpstate

root@apu1a:~/rate_limiters# ethtool -i eth0
driver: r8169
version: 2.3LK-NAPI
firmware-version: rtl_nic/rtl8168e-2.fw
bus-info: 0000:01:00.0
supports-statistics: yes
supports-test: no
supports-eeprom-access: no
supports-register-dump: yes
supports-priv-flags: no