[lxc-devel] lxc final thesis

[Daniel Lezcano]

On 03/18/2011 06:40 PM, Farcasi Ana-Maria wrote:
> Hello,
>
> As mentioned in our previous email, we were having issues getting bandwidth
> limitation working on cgroup ( with net_cls ) and tc. We've been running
> various tests and scenarios but found no way to enable proper limitation.
> Throughout our testing we've created a virtual machine running a 2.6.35
> kernel where the limitation was indeed working.
>
> We've browsed recent commits in the Linux-2.6 kernel source code and
> discovered that ever since version 2.6.35 (actually ever since this
> commit[1] was integrated), there is a change in getting the packet classid -
> the classid is stored and read as a member of a struct sock. As this is also
> used by LXC, it means that ever since 2.6.35, bandwidth limitation using tc
> is working for cgroups.
>
> In order to prove this, we've compiled the latest 2.6.34 and 2.6.35 kernels
> (2.6.34.8 and 2.6.35.11). We've used tc, cgroup (net_cls) and iperf to test
> this.
>
> On the latter version ( 2.6.35.11 ) the limitation is working accordingly,
> while on the former ( 2.6.34.8 ) the limitation is not working at all. We
> believe the above mentioned commit[1] is responsible for solving this issue
> and post-2.6.35 kernels should have no problems using cgroup-based bandwidth
> limitation (for example, within LXC).
>
> We were thinking whether it would be a good idea to integrate an option for
> bandwidth limitation into an LXC container configuration file (such as
> lxc.network.bwlimit). This would allow a rapid setup of an LXC container and
> network limitation. This could, of course, be set up using tc (it would take
> a bit more effort, though). What do you think?


Hi Irina and Ana,

Thanks for investigating this, it is very useful.

Adding the setup to lxc is a good idea and I will be happy to merge 
upstream your modifications to take into account the bandwidth limitations.

As far as I remember the bandwidth limitations is for download and 
upload no ? If it is the case, I would recommend to use the options:

lxc.network.bandwidth.download = value
lxc.network.bandwidth.upload = value

I thought another feature would be interesting, the network 
provisioning. I don't if it is supported by the kernel (I don't think 
so) but if we can assign for example 1GB of download/upload to the 
container and when it is reached the network become stuck until we add 
more provisioning, that could be very useful. What do you think ?

Thanks
   -- Daniel

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