Re: tc shown rate larger than ceil (was "Weird rate in HTB")

Linux Advanced Routing and Traffic Control

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Andy - Thanks!

I took the ethtool path, and turned off tcp segmentation on that nic; I was unsure how to set the HTB MTU - I use shorewall on a Gentoo system.

It has definitely made a difference. The highest rate I see is 282312bits on a line with a ceil of 282000bits - and that is with 24pps, which, according to your previous email . . . would be right in line with what it should be.

Giants have fallen off, but are not completely eliminated. Is this something I should be concerned with (having giants)? Would setting the HTB MTU be more elegant? I have avoided creating my own tc script, and have been using shorewall's internals . . . but if utilizing the HTB MTU setting is "better", I will dive in and try to write a script that does the same thing as shorewall.

Stone

On Aug 1, 2007, at 1:43 PM, Andy Furniss wrote:

Stonie Cooper wrote:
An earlier exchange about someone seeing the rate larger than the ceiling is posted below. Andy explained the reason for the "above ceiling" rate in Daniel's output . . . but I just saw an example that doesn't fit.
 >> tc output >>
class htb 1:14 parent 1:1 leaf 14: prio 1 quantum 3072 rate 256000bit ceil 282000bit burst 1820b/8 mpu 0b overhead 0b cburst 1851b/8 mpu 0b overhead 0b level 0
Sent 2639448 bytes 1128 pkt (dropped 0, overlimits 0 requeues 0)
rate 325360bit 17pps backlog 0b 25p requeues 0
lended: 981 borrowed: 122 giants: 1155

It's because you have giants - possibly because your nic does tcp segmentation offload so locally generated traffic goes through htb as big chunks before it gets segmented down to the nic's mtu.

You can check/turn that off with ethtool -k or you could use htb's mtu parameter for each rate (I'm not sure if you need to do ceils aswell) which makes the granularity of the rate table bigger so it can handle the larger mtu.

Andy.

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