On 02/08/2013 12:07 PM, Dennis Jacobfeuerborn wrote: > 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. So after further digging I finally stumbled upon the solution. The reason this wasn't working is that I'm running this in a xen guest and apparently the tx checksum offloading screws things up. I removed the burst/cburst options again and instead issued a "ethtool -K eth0 tx off" and now the traffic is limited at the expected 200mbit. Regards, Dennis -- To unsubscribe from this list: send the line "unsubscribe lartc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
