Re: [PATCH V1 0/6] fast qom tree get

[Markus Armbruster <armbru@redhat.com>]

Steven Sistare <steven.sistare@oracle.com> writes:

> On 4/28/2025 4:04 AM, Markus Armbruster wrote:
>> Steven Sistare <steven.sistare@oracle.com> writes:
>> 
>>> On 4/9/2025 3:39 AM, Markus Armbruster wrote:
>>>> Hi Steve, I apologize for the slow response.
>>>>
>>>> Steve Sistare <steven.sistare@oracle.com> writes:
>>>>
>>>>> Using qom-list and qom-get to get all the nodes and property values in a
>>>>> QOM tree can take multiple seconds because it requires 1000's of individual
>>>>> QOM requests.  Some managers fetch the entire tree or a large subset
>>>>> of it when starting a new VM, and this cost is a substantial fraction of
>>>>> start up time.
>>>>
>>>> "Some managers"... could you name one?
>>>
>>> My personal experience is with Oracle's OCI, but likely others could benefit.
>> 
>> Elsewhere in this thread, we examined libvirt's use qom-get.  Its use of
>> qom-get is also noticably slow, and your work could speed it up.
>> However, most of its use is for working around QMP interface
>> shortcomings around probing CPU flags.  Addressing these would help it
>> even more.
>> 
>> This makes me wonder what questions Oracle's OCI answers with the help
>> of qom-get.  Can you briefly describe them?
>> 
>> Even if OCI would likewise be helped more by better QMP queries, your
>> fast qom tree get work might still be useful.
>
> We already optimized our queries as a first step, but what remains is still
> significant, which is why I submitted this RFE.

I understand your motivation.  I'd like to learn more on what OCI
actually needs from QMP, to be able to better serve it and potentially
other management applications.