Re: [PATCH v10 0/8] hmp, qmp: Add commands to introspect virtio devices

[Christian Schoenebeck]

On Montag, 6. Dezember 2021 17:09:45 CET Jonah Palmer wrote:
> On 12/6/21 08:50, Christian Schoenebeck wrote:
> > On Montag, 6. Dezember 2021 13:43:18 CET Jonah Palmer wrote:
> >> This series introduces new QMP/HMP commands to dump the status of a
> >> virtio device at different levels.
> >> 
> >> [Jonah: Rebasing previous patchset from Nov. 10 (v9). Original patches
> >> 
> >>   are by Laurent Vivier from May 2020.
> >>   
> >>   Rebase from v9 to v10 includes reformatting virtio.json examples and
> >>   command structures for better consistency. Also removed all enums from
> >>   virtio.json and replaced their purpose with string literals.
> >>   
> >>   Removed @ndescs from VirtioQueueElement, as the number of descriptors
> >>   can be inferred from the length of the @descs chain.
> >>   
> >>   Lastly, removed the examples in hmp-commands-info.hx to fix
> >>   'inconsistent
> >>   literal block quoting' warning from Sphinx.]
> > 
> > I have not followed the entire discussion. AFAICS this is intended to
> > monitor status information on virtio level only, like virtqueue fill
> > status, etc.
> > 
> > One thing that I am looking for is monitoring device specific information
> > above virtio level, e.g. certain performance numbers or statistics that
> > only make sense for the specific device. That would not fit into any of
> > these commands, right?
> > 
> > Best regards,
> > Christian Schoenebeck
> 
> Correct. These are just one-shot commands that dump information on virtio
> devices (including vhosts), their virtqueues, and virtqueue elements as they
> are at the time of the command.
> 
> Jonah

What I would find useful though on this virtio level: also being able to query 
the maximum and average fill state of the two ring buffers of each virtqueue. 
That would allow to identify performance bottlenecks.

Best regards,
Christian Schoenebeck