Re: [virtio-dev] RE: [virtio-comment] RE: [PATCH v13] virtio-net: support inner header hash

[Heng Qi <hengqi@linux.alibaba.com>]

å 2023/4/26 äå10:24, Parav Pandit åé:
> > From: Heng Qi <hengqi@linux.alibaba.com>
> > Sent: Wednesday, April 26, 2023 10:04 AM
> > Yes, but that seems like a tiny cost, and the cvq command-related structure is
> > much simpler.
> Current structure size is 24 bytes.
> This size becomes multiplier with device count scale to be always available and rarely changes.
>
> As we add new features such device capabilities grow making the multiplier bigger.
> For example
> a. flow steering capabilities (how many flows, what mask, supported protocols, generic options)
> b. hds capabilities
> c. counter capabilities (histogram based, which error counters supported, etc)
> d. which new type of tx vq improvements supported.
> e. hw gro context count supported
>
> May be more..
>
> Depending on the container/VM size certain capabilities may change from device to device.
> Hence it is hard to deduplicate them at device level.

This makes sense. In general, we should be careful about adding things 
to the device space unless the benefit is non-trivial.

Thanks.

> Therefore, ability to query them over a non_always_available transport is preferred choice from the device.
>
> A driver may choose to cache it if its being frequently accessed or ask device when needed.
> Even when it's cached by driver, it is coming from the component that doesnât have transport level timeouts associated with it.