On 06/08/2018 05:58 AM, Trapp, Michael wrote:
On 08.06.18, 10:31, "Daniel P. Berrangé" <berrange@xxxxxxxxxx> wrote: On Thu, Jun 07, 2018 at 04:23:32PM -0600, Jim Fehlig wrote: > On 06/07/2018 09:42 AM, Trapp, Michael wrote: > > I fully understand the requirements regarding coding style and the way the changes should be split and discussed in detail, > > but may I ask you to provide some general feedback about the basic concept and if this an option at all before we start discussing the details. > > vhostmd already supports 'vbd' and 'xenstore' as transports for the metric > data. Adding another virtio-channel based transport is a great idea IMO. > > WRT writing the data to the various channels, I suppose it is possible to do > that even if there is no (immediate) recipient for the data? The vbd and > xenstore transports don't have a protocol so to speak. The data is simply > written to the disk or xenstore node regardless if there is someone to > consume it. Can the virtio transport work the same? If so, that would > alleviate the need for polling all the fds and the static list of > epoll_event. In virtio_metrics_update() we could simply connect to all the > channels, write the data, close them, and repeat on the next update period > (which is every 5sec by default).Why push it to the guest at a fixed frequency, rather than just letting theguest query the host at whatever rate it feels it needs ?content on virtio channel is not discarded. I've setup a simple test and a continuous write on host side blocks when ~123kB are buffered from OS + QEMU.
Ok, we definitely don't want to mindlessly stuff data in the channel from the host side :-).
A delayed read on the VM side contains the whole buffered data. Looks like the virtio based approach needs a query from the VM to guarantee that the VM get's the current metrics.
Agreed. Would be nice to avoid the MAX_CHANNELS build-time limit. If nothing else it could be a config file option.
Regards, Jim _______________________________________________ virt-tools-list mailing list virt-tools-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/virt-tools-list
