[openstack-dev] rxtx factor in instance types

Trey Morris trey.morris at RACKSPACE.COM
Thu Jan 31 18:34:05 UTC 2013

Oops, I fail at email..


Your use case is similar to how we use it. The idea is that the instance_types rxtx_factor is multiplied by the rxtx_base on networks to equal the rxtx_cap which ends up as a meta characteristic of a vif in the network_info model.

For example if you have a network with a 1024kb/s rxtx_base, you can have several different instance types with rxtx_factors of 1.0, 2.0, 4.0, 10.0…. etc. When the network_info object is crafted by the network manager, it multiplies the two and stores the result in the meta field of vif. If you have multiple networks, they can have different rxtx_base values, and this will be reflected in the rxtx_cap for the resulting vifs. At this point anything that has access to the network_info object can grab the values from vif.get_meta('rxtx_cap'). As vish pointed out, the xen vif driver passes the rxtx_cap to xen in the process of creating vifs on the hypervisor.


On Jan 30, 2013, at 8:32 PM, Vishvananda Ishaya wrote:

Hi phil,

It is used to generate the rxtx_cap in the network_info cache which is in turn used to generate qos params in xenapi in:


I don't believe it is used in the other drivers at all.

tr3buchet or _cerberus_ might be able to add a bit more detail


On Jan 30, 2013, at 1:43 PM, "Day, Phil" <philip.day at hp.com<mailto:philip.day at hp.com>> wrote:

Hi Folks,

Can anyone point me to where the rxtx factor of an instance type is currently used in the code please ?

I was thinking about the use case of having instance types which are differentiated by their network bandwidth, and how that could be accommodated in a scheduler filter and passed down to the virt layer for cgroup configuration, and the rxtx factor seems to be the obvious starting point – but I was struggling to see how its already used.

Has anyone else looked at this as an issue ?

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