Re: [virtio-dev] [PATCH v14] virtio-net: support the virtqueue coalescing moderation

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Apr 05, 2023 at 04:54:44PM +0200, Halil Pasic wrote:
> On Wed, 5 Apr 2023 05:12:12 -0400
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > > > it's not necessarily an identifier. can be e.g. just 0 for all vqs.
> > > > whatever the device needs.  
> > > For driver its just an id, content doesn't matter.  
> > 
> > No, this value might or might not be somehow related to the vq but it
> > does not have to identify it. So it's some data, not an id.  Let's try
> > to use words for what they mean in english not try to come up with our
> > own language.
> 
> I agree with Michael wholeheartedly, we should try to use words for what
> they mean in English, especially in Computer Science English, and even
> try to pick the most fitting and least ambiguous option if multiple
> options are possible.
> 
> In that spirit I would say that "queue_notify_data" is actually a magic
> cookie. https://en.wikipedia.org/wiki/Magic_cookie A possible name
> or abbreviation would be vqn_cookie like "a virtqueue
> notification cookie" (I'm not sure about mixing in the direction, but
> this is only about driver -> device notifications). 
> 
> 
> And then 
> 
> le32 {
>         vqn : 16;
>         next_off : 15;
>         next_wrap : 1;
> };
> 
> could become something like
> 
> struct vq_notif_data {
>         union {
> 		le16 vqn_cookie;
> 		le16 vq_index;
> 	};
>         le16 {
> 		next_off : 15;
>         	next_wrap : 1;
> 	};
> };
> 
> BTW since "identifier" and "unique identifier" are not the same, in my
> opinion "identifier" is still viable, if we explain that it is called
> identifier because the idea behind that field is to be used to identify
> the queue, but that there is in fact no requirement on selectivity let
> alone uniqueness.
> 
> 
> Regards,
> Halil 
> 

Well "identifier" seems to come from "identity" meaning "same" so I
think yes, it implies a 1:1 relationship.
And more importantly, it might not identify the queue, there is
in fact no requirement on how it is used at all.

-- 
MST