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

[Sebastian Moeller <moeller0@gmx.de>]

[-- Attachment #1: Type: text/plain, Size: 7460 bytes --]

Well the idea would be to scale the buffer to cover, say Xms at the configured bandwidth, so HTB could deal with CPU stalls up to X-Yms (with Y << X)... We just switched sqm-scripts to automatically scale the buffering to 1ms....
Would be interested to learn whether that would increase HTB's utilisation?


On December 30, 2018 11:36:27 PM GMT+01:00, Pete Heist <pete@heistp.net> wrote:
>The experiments I did with those didn’t yield great results, with
>changing a value by one MTU sometimes causing sudden throughput or
>inter-flow latency increases, with the tradeoffs not being clear. I’m
>afraid admins could easily cause problems fiddling with these.
>Fortunately most customer facing routers have aggregate bitrates that
>an APU1 can handle even with default htb, or cake. I also appreciate
>that such settings don’t exist in cake… :)
>
>> On Dec 30, 2018, at 10:51 PM, Sebastian Moeller <moeller0@gmx.de>
>wrote:
>> 
>> Hi Pete,
>> 
>> you might want to have a look at htb's burst and cburst parameters,
>as these should allow to trade in latency under load for bandwidth
>utilization.
>> 
>> 
>> Best Regards
>> 	Sebastian
>> 
>>> On Dec 30, 2018, at 21:42, Pete Heist <pete@heistp.net> wrote:
>>> 
>>> It’s a bit more complicated than this. It looks like the htb rate
>limiter is different in that as rates increase the actual rate starts
>to deviate from the specified rate early on, but it rather gracefully
>handles the “out of CPU” situation, where it still maintains control of
>the queue, just gradually fails to meet the rate specified by greater
>and greater percentages.
>>> 
>>> Instead of a single flow test with iperf3, here are rates that each
>limiter can reach on egress of both apu1a interfaces during an rrul_be
>test:
>>> 
>>> # - max limit on APU for one-armed routing, rrul_be test 4+4 flows
>(firewall on):
>>> #   - cake: 210mbit
>>> #   - htb+fq_codel: 93%@100mbit, 90%@200mbit, 84%@300mbit,
>72%@400mbit, 59%@500mbit
>>> #   - hfsc+fq_codel: 310mbit
>>> #   - hfsc+cake: 300mbit
>>> 
>>> The numbers for cake and hfsc are right before loss of queue, and
>with htb the queue isn’t lost even at 500mbit, for example, just the
>actual rate is only 59% of what was specified.
>>> 
>>> I really need to graph the specified rate vs the actual rate,
>inter-flow and intra-flow latency, stepped 25mbit at a time. I think it
>would be interesting, so this is on my todo list if there’s time after
>the ISP config gets done.
>>> 
>>>> On Dec 28, 2018, at 1:17 AM, Pete Heist <pete@heistp.net> wrote:
>>>> 
>>>> 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
>>>> 
>>> 
>>> _______________________________________________
>>> Cake mailing list
>>> Cake@lists.bufferbloat.net
>>> https://lists.bufferbloat.net/listinfo/cake
>> 

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

[-- Attachment #2: Type: text/html, Size: 7669 bytes --]