Re: HTB limiting working for single big download but not for many small ones

[Dennis Jacobfeuerborn <dennisml@conversis.de>]

On 02/07/2013 06:57 PM, Dennis Jacobfeuerborn wrote:
> Hi,
> I've run into problems trying to limit the overall download bandwidth for a
> webserver. This is the code I'm using:
> 
> tc qdisc add dev eth0 root handle 1: htb default 30
> tc class add dev eth0 parent 1: classid 1:1 htb rate 200mbit ceil 200mbit
> tc filter add dev eth0 protocol ip parent 1:0 prio 1 u32 match ip sport 80
> 0xffff flowid 1:1
> 
> The problem is that when I test this with a single connection downloading a
> large file I can see the download speed according to the specified limit
> (in this case 200mbit).
> When I use this code on a production system that receives several thousand
> small downloads from an nginx server however I see the following:
> 
> # tc -s -d class show dev eth0
> class htb 1:1 root prio 0 quantum 200000 rate 200000Kbit ceil 200000Kbit
> burst 101600b/8 mpu 0b overhead 0b cburst 101600b/8 mpu 0b overhead 0b level 0
>  Sent 246544581544 bytes 55302789 pkt (dropped 1614680, overlimits 0
> requeues 0)
>  rate 636728Kbit 16228pps backlog 0b 229p requeues 0
>  lended: 55302560 borrowed: 0 giants: 51516908
>  tokens: -3729 ctokens: -3729
> 
> The rate is over 600mbit so I'm not sure why the traffic isn't limited to
> the 200mbit specified. Is there something else I need to take into account
> here to make this work?

I've now experimented with burst/cburst but either I end up with a rate way
below 200mbit or easily exceeding 600mbit. Apparently the actual 200mbit
limit is just ignored.

Regards,
  Dennis