Re: [PATCH v4 0/7] Move memory listener register to vhost_vdpa_init

[Markus Armbruster <armbru@redhat.com>]

Jonah Palmer <jonah.palmer@oracle.com> writes:

[...]

>> I think I finally know enough to give you constructive feedback.
>> 
>> Your commit messages should answer the questions I had.  Specifically:
>> 
>> * Why are we doing this?  To shorten guest-visible downtime.
>> 
>> * How are we doing this?  We additionally pin memory before entering the
>>   main loop.  This speeds up the pinning we still do in the main loop.
>> 
>> * Drawback: slower startup.  In particular, QMP becomes
>>   available later.
>> 
>> * Secondary benefit: main loop responsiveness improves, in particular
>>   QMP.
>> 
>> * What uses of QEMU are affected?  Only with vhost-vDPA.  Spell out all
>>    the ways to get vhost-vDPA, please.
>> 
>> * There's a tradeoff.  Show your numbers.  Discuss whether this needs to
>>   be configurable.
>> 
>> If you can make a case for pinning memory this way always, do so.  If
>> you believe making it configurable would be a good idea, do so.  If
>> you're not sure, say so in the cover letter, and add a suitable TODO
>> comment.
>> 
>> Questions?
>
> No questions, understood.
>
> As I was writing the responses to your questions I was thinking to 
> myself that this stuff should've been in the cover letter / commit 
> messages in the first place.
>
> Definitely a learning moment for me. Thanks for your time on this Markus!

You're welcome!