Re: [PATCH V2 vfio 00/14] Add migration PRE_COPY support for mlx5 driver

Yishai Hadas
2022-12-04T11:54:55Z

On 02/12/2022 10:57, Tian, Kevin wrote:
>> From: Yishai Hadas <yishaih@nvidia.com>
>> Sent: Thursday, December 1, 2022 11:29 PM
>>
>> In mlx5 driver we could gain with this series about 20-30 percent
>> improvement
>> in the downtime compared to the previous code when PRE_COPY wasn't
>> supported.
>>
> Curious to see more data here.
>
> what is the workload/configuration?
We tested with multiple workloads which were varied by the number of
allocated resources, number of VFs on the VM, busy or idle device
depending on some traffic that runs in the background, etc.
>
> What is the size of the full state and downtime w/o PRECOPY?

It depends on the amount of the allocated resources that were already
opened upon the migration, and the other workloads parameters as
mentioned above.

The downtime gain was mainly achieved by sending the initial/middle
states having the metadata without regard to the size.

>
> with PRECOPY what is the size of initial/middle/final states?

Generally saying, the initial state may include metadata on the current
state, the middle states may hold 'diff' compared to the
initial/previous ones and in most cases may be smaller, the final state
holds the data itself and may be larger.

Yishai