Re: [PATCH vfio 0/7] Enhances the vfio-virtio driver to support live migration

[Yishai Hadas <yishaih@nvidia.com>]

On 28/10/2024 18:23, Jason Gunthorpe wrote:
> On Mon, Oct 28, 2024 at 10:13:48AM -0600, Alex Williamson wrote:
>> On Sun, 27 Oct 2024 12:07:44 +0200
>> Yishai Hadas <yishaih@nvidia.com> wrote:
>> If the virtio spec doesn't support partial contexts, what makes it
>> beneficial here?
> 
> It stil lets the receiver 'warm up', like allocating memory and
> approximately sizing things.
> 
>> If it is beneficial, why is it beneficial to send initial data more than
>> once?
> 
> I guess because it is allowed to change and the benefit is highest
> when the pre copy data closely matches the final data..
> 
> Rate limiting does seem better to me
> 
> Jason


Right, given that the device state is likely to remain mostly unchanged 
over a certain period, using a rate limiter could be a sensible approach.

So, in V1, I plan to replace the hard-coded limit value of 128 with a 
rate limiter by reporting no data available for some time interval after 
the previous call.

I would start with a one second interval, which seems to be reasonable 
for that kind of device.

Yishai