On 06/08/2018 02:30 AM, Daniel P. Berrangé 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 the
guest query the host at whatever rate it feels it needs ?
The other transports work that way, but in those cases the guests use the same
source on the host, e.g. a ramdisk for vbd. For virtio where the source is a
per-guest channel on the host, I suppose it's best to only send the metrics when
the guest asks for them.
Regards,
Jim
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