Question about the Qos support status for different type interfaces
Hi there, I have a question about the Qos support status for different type interfaces. Some types of interface do not support Qos, such as hostdev, user type, mcast type, but the behavior are different, for hostdev, the guest can not start with a meaningful error message, but for other types, vm can start successfully with a warning message in the libvirtd log. I doubt that if it is necessary to keep the behavior consistent for these different types? There are 2 history bugs for them, I should have thought further and asked early when testing the bugs. Bug 1319044 <https://bugzilla.redhat.com/show_bug.cgi?id=1319044> - log error when <bandwidth> requested on a <interface type='hostdev'> Bug 1524230 <https://bugzilla.redhat.com/show_bug.cgi?id=1524230> - vhostuser type interface do not support bandwidth, but no warning message Thank you for looking into this and very appreciate your feedback! 1. start vm with user type interface set with Qos: <interface type='user'> <mac address='52:54:00:3e:ec:14'/> <bandwidth> <inbound average='1000' peak='5000' burst='5120'/> <outbound average='128' peak='256' burst='256'/> </bandwidth> <model type='rtl8139'/> <address type='pci' domain='0x0000' bus='0x07' slot='0x01' function='0x0'/> </interface> # cat /var/log/libvirt/libvirtd.log | grep bandwidth 2021-03-26 10:47:11.452+0000: 20185: warning : qemuBuildInterfaceCommandLine:8223 : setting bandwidth on interfaces of type 'user' is not implemented yet 2. start with hostdev type interface with Qos setting: <interface type='hostdev' managed='yes'> <mac address='52:54:00:07:27:b0'/> <source> <address type='pci' domain='0x0000' bus='0x82' slot='0x10' function='0x6'/> </source> <bandwidth> <inbound average='1000' peak='5000' burst='5120'/> <outbound average='128' peak='256' burst='256'/> </bandwidth> <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/> </interface> # virsh start rh error: Failed to start domain 'rh' error: unsupported configuration: interface 52:54:00:07:27:b0 - bandwidth settings are not supported for hostdev interfaces ------- Best Regards, Yalan Zhang IRC: yalzhang
On 3/26/21 12:31 PM, Yalan Zhang wrote:
Hi there,
I have a question about the Qos support status for different type interfaces. Some types of interface do not support Qos, such as hostdev, user type, mcast type, but the behavior are different, for hostdev, the guest can not start with a meaningful error message, but for other types, vm can start successfully with a warning message in the libvirtd log. I doubt that if it is necessary to keep the behavior consistent for these different types?
There are 2 history bugs for them, I should have thought further and asked early when testing the bugs. Bug 1319044 <https://bugzilla.redhat.com/show_bug.cgi?id=1319044>- log error when <bandwidth> requested on a <interface type='hostdev'> Bug 1524230 <https://bugzilla.redhat.com/show_bug.cgi?id=1524230>- vhostuser type interface do not support bandwidth, but no warning message
Thank you for looking into this and very appreciate your feedback!
The reason is historical baggage - as usual. When QoS was fist introduced it supported only a very few interface types. Soon we've learned that users put XML snippets in for other types too. Back then we had no validation callbacks => we could not reject such XMLs because we did not do it from the beginning. So there might be some domain XMLs still that contain QoS for unsupported type and those would be lost if libvirt started rejecting such XMLs. With validation callbacks things are a bit better - the domain would not be lost on libvirtd upgrade; though it would still be unable to start. I'm not sure that's much better. Hence, we're keeping status quo. I'm open for ideas though. Michal
Hi Michal, Thank you for the clarification. ------- Best Regards, Yalan Zhang IRC: yalzhang On Fri, Mar 26, 2021 at 8:19 PM Michal Privoznik <mprivozn@redhat.com> wrote:
On 3/26/21 12:31 PM, Yalan Zhang wrote:
Hi there,
I have a question about the Qos support status for different type interfaces. Some types of interface do not support Qos, such as hostdev, user type, mcast type, but the behavior are different, for hostdev, the guest can not start with a meaningful error message, but for other types, vm can start successfully with a warning message in the libvirtd log. I doubt that if it is necessary to keep the behavior consistent for these different types?
There are 2 history bugs for them, I should have thought further and asked early when testing the bugs. Bug 1319044 <https://bugzilla.redhat.com/show_bug.cgi?id=1319044>- log error when <bandwidth> requested on a <interface type='hostdev'> Bug 1524230 <https://bugzilla.redhat.com/show_bug.cgi?id=1524230>- vhostuser type interface do not support bandwidth, but no warning message
Thank you for looking into this and very appreciate your feedback!
The reason is historical baggage - as usual. When QoS was fist introduced it supported only a very few interface types. Soon we've learned that users put XML snippets in for other types too. Back then we had no validation callbacks => we could not reject such XMLs because we did not do it from the beginning. So there might be some domain XMLs still that contain QoS for unsupported type and those would be lost if libvirt started rejecting such XMLs.
With validation callbacks things are a bit better - the domain would not be lost on libvirtd upgrade; though it would still be unable to start. I'm not sure that's much better.
Hence, we're keeping status quo. I'm open for ideas though.
Michal
participants (2)
-
Michal Privoznik -
Yalan Zhang