On 8/9/2023 7:49 AM, Eugenio Perez Martin wrote:> On Wed, Aug 9, 2023 at 2:56?PM Si-Wei Liu <si-wei.liu at oracle.com>
wrote:
>> Following patchset introduces dedicated group for descriptor table to
>> reduce live migration downtime when passthrough VQ is being switched
>> to shadow VQ. As this RFC set is to seek early feedback on the uAPI
>> and driver API part, for now there's no associated driver patch
consuming
>> the API. As soon as the support is in place on both hardware device and
>> driver, performance data will be show using real hardware device. The
>> target goal of this series is to reduce the SVQ switching overhead
>> to less than 300ms on a ~100GB guest with 2 non-mq vhost-vdpa devices.
>>
> I would expand the cover letter with something in the line of:
> The reduction in the downtime is thanks to avoiding the full remap in
> the switching.
Sure, will add in the next.
>
>> The plan of the intended driver implementation is to use a dedicated
>> group (specifically, 2 in below table) to host descriptor table for
>> all data vqs, different from where buffer addresses are contained (in
>> group 0 as below). cvq does not have to allocate dedicated group for
>> descriptor table, so its buffers and descriptor table would always
>> belong to a same group (1).
>>
>>
>> | data vq | ctrl vq
>> ==============+==========+==========>> vq_group | 0 |
1
>> vq_desc_group | 2 | 1
>>
>>
> Acked-by: Eugenio P?rez <eperezma at redhat.com>
Thanks!
-Siwei
>
>
>> ---
>>
>> Si-Wei Liu (3):
>> vdpa: introduce dedicated descriptor group for virtqueue
>> vhost-vdpa: introduce descriptor group backend feature
>> vhost-vdpa: uAPI to get dedicated descriptor group id
>>
>> drivers/vhost/vdpa.c | 27 +++++++++++++++++++++++++++
>> include/linux/vdpa.h | 11 +++++++++++
>> include/uapi/linux/vhost.h | 8 ++++++++
>> include/uapi/linux/vhost_types.h | 5 +++++
>> 4 files changed, 51 insertions(+)
>>
>> --
>> 1.8.3.1
>>