From mboxrd@z Thu Jan  1 00:00:00 1970
From: Brian Rak <brak@gameservers.com>
Date: Tue, 11 Mar 2014 16:48:06 +0000
Subject: tc burst size rollover
Message-Id: <531F3E46.4050503@gameservers.com>
List-Id: <lartc.vger.kernel.org>
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To: lartc@vger.kernel.org

I'm seeing some weird behavior when I'm trying to add some htb queue 
settings with large burst sizes.  It seems that if I specify a burst 
size over 3355443kb, the number rolls over.  For example:

# tc class add dev vnet1 parent 1: classid 1:1 htb rate 12500kbps ceil 
125000kbps burst 3355444kb
# tc class show dev vnet1  parent 1:
class htb 1:1 root prio 0 rate 100000Kbit ceil 1000Mbit burst 812b 
cburst 1375b

Is there supposed to be a limitation here? I can't seem to find anything 
in the documentation talking about it.

I've tested this with iproute2-3.12.0 on 3.13.1-1.el6.elrepo.x86_64. 
This is the full set of commands I was using (these are what libvirt 
applies by default):

tc qdisc del dev vnet1 root
tc qdisc del dev vnet1 ingress
tc qdisc add dev vnet1 root handle 1: htb default 1
tc class add dev vnet1 parent 1: classid 1:1 htb rate 12500kbps ceil 
125000kbps burst 3355444kb
tc class show dev vnet1  parent 1:


Ultimately, I'm trying to allow bursts at 1000mbit up to 100GB or so, 
then restrict things to a lower speed.  I'm not aware of any way to do 
this aside from using a large burst size.