Re: [LARTC] TC (HTB) doesn't work well when network is congested?

[William Xu <wxu@max-t.com>]

Thank you, Peter,

After changing CONFIG_HZ to 1000, TC works much better. I still need to 
limit the total bandwidth
to 110MB/s (about 90% of 125MB/s), but that's normal I guess.

Thanks again,
william
Peter Rabbitson wrote:

> William Xu wrote:
>
>> Hi Peter, thanks for looking at this.
>>
>> Here are the information I got after running tests. The client1 got 
>> 7MB/s instead of 40MB/s for SEND,
>> and 40MB/s for RECV during the test.
>>
>> Thanks,
>> william
>>
>> # ip link show
>>
>> ...
>> 5: eth2: <BROADCAST,MULTICAST,UP,LUP> mtu 9000 qdisc htb qlen 1000
>>    link/ether 00:e0:ed:04:9f:a2 brd ff:ff:ff:ff:ff:ff
>> ...
>> 12: ifb0: <BROADCAST,NOARP,UP,LUP> mtu 9000 qdisc htb qlen 32
>>    link/ether f2:f2:77:f9:cf:30 brd ff:ff:ff:ff:ff:ff
>>
>> #tc qdisc show
>> qdisc pfifo_fast 0: dev eth0 root bands 3 priomap  1 2 2 2 1 2 0 0 1 
>> 1 1 1 1 1 1 1
>> qdisc ingress ffff: dev eth2 ----------------
>> qdisc htb 1: dev eth2 r2q 100 default 30 direct_packets_stat 0
>> qdisc pfifo_fast 0: dev eth3 root bands 3 priomap  1 2 2 2 1 2 0 0 1 
>> 1 1 1 1 1 1 1
>> qdisc pfifo_fast 0: dev eth4 root bands 3 priomap  1 2 2 2 1 2 0 0 1 
>> 1 1 1 1 1 1 1
>> qdisc pfifo_fast 0: dev eth5 root bands 3 priomap  1 2 2 2 1 2 0 0 1 
>> 1 1 1 1 1 1 1
>> qdisc pfifo_fast 0: dev eth6 root bands 3 priomap  1 2 2 2 1 2 0 0 1 
>> 1 1 1 1 1 1 1
>> qdisc pfifo_fast 0: dev eth7 root bands 3 priomap  1 2 2 2 1 2 0 0 1 
>> 1 1 1 1 1 1 1
>> qdisc pfifo_fast 0: dev eth8 root bands 3 priomap  1 2 2 2 1 2 0 0 1 
>> 1 1 1 1 1 1 1
>> qdisc htb 1: dev ifb0 r2q 100 default 30 direct_packets_stat 0
>>
>> #tc -s -d class show dev ifb0
>> class htb 1:10 parent 1:1 prio 0 quantum 200000 rate 320000Kbit ceil 
>> 960000Kbit burst 169000b/64 mpu 0b overhead 0b cburst 489000b/64 mpu 
>> 0b overhead 0b level 0
>> Sent 2366125838 bytes 928639 pkt (dropped 0, overlimits 0 requeues 0)
>> rate 0bit 0pps backlog 0b 0p requeues 0
>> lended: 925807 borrowed: 2832 giants: 0
>> tokens: 4224 ctokens: 4075
>>
>> class htb 1:1 root rate 960000Kbit ceil 960000Kbit burst 489000b/64 
>> mpu 0b overhead 0b cburst 489000b/64 mpu 0b overhead 0b level 7
>> Sent 36927678674 bytes 6132723 pkt (dropped 0, overlimits 0 requeues 0)
>> rate 2672bit 1pps backlog 0b 0p requeues 0
>> lended: 1131873 borrowed: 0 giants: 0
>> tokens: 4074 ctokens: 4074
>>
>> class htb 1:30 parent 1:1 prio 1 quantum 200000 rate 640000Kbit ceil 
>> 960000Kbit burst 328960b/64 mpu 0b overhead 0b cburst 489000b/64 mpu 
>> 0b overhead 0b level 0
>> Sent 34561552836 bytes 5204084 pkt (dropped 44, overlimits 0 requeues 0)
>> rate 528bit 0pps backlog 0b 0p requeues 0
>> lended: 4075043 borrowed: 1129041 giants: 0
>> tokens: 4108 ctokens: 4074
>>
>> #tc -s -d class show dev eth2
>> class htb 1:10 parent 1:1 prio 0 quantum 200000 rate 320000Kbit ceil 
>> 960000Kbit burst 169000b/64 mpu 0b overhead 0b cburst 489000b/64 mpu 
>> 0b overhead 0b level 0
>> Sent 12092794712 bytes 1544210 pkt (dropped 0, overlimits 0 requeues 0)
>> rate 56bit 0pps backlog 0b 0p requeues 0
>> lended: 1543687 borrowed: 523 giants: 0
>> tokens: 4224 ctokens: 4075
>>
>> class htb 1:1 root rate 960000Kbit ceil 960000Kbit burst 489000b/64 
>> mpu 0b overhead 0b cburst 489000b/64 mpu 0b overhead 0b level 7
>> Sent 36872760531 bytes 7346321 pkt (dropped 0, overlimits 0 requeues 0)
>> rate 288bit 0pps backlog 0b 0p requeues 0
>> lended: 40477 borrowed: 0 giants: 0
>> tokens: 4073 ctokens: 4073
>>
>> class htb 1:30 parent 1:1 prio 1 quantum 200000 rate 640000Kbit ceil 
>> 960000Kbit burst 328960b/64 mpu 0b overhead 0b cburst 489000b/64 mpu 
>> 0b overhead 0b level 0
>> Sent 24779965819 bytes 5802111 pkt (dropped 0, overlimits 0 requeues 0)
>> rate 176bit 0pps backlog 0b 0p requeues 0
>> lended: 5762157 borrowed: 39954 giants: 0
>> tokens: 4109 ctokens: 4073
>>
>>
>
> The setup looks good. There are only two things that come to mind - 
> you have problems with TSO, or your clock is too slow. For the first 
> use ethtool -K to disable all 6 offloading parameters. For the second 
> check what is the value of CONFIG_HZ in the current kernel config 
> (/boot/config-<your-kernel-version>), and if it is less than 1000 this 
> might be your problem as well. If none of those help - I am out of 
> ideas, hopefully someone else can help you.
>
> Peter


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