Re: [PATCH v3 00/24] Multifd 🔀 device state transfer support with VFIO consumer

[Peter Xu]

On Thu, Dec 05, 2024 at 10:27:09PM +0100, Cédric Le Goater wrote:

[...]

> > Important note:
> > 4 VF benchmarks were done with commit 5504a8126115
> > ("KVM: Dynamic sized kvm memslots array") and its revert-dependencies
> > reverted since this seems to improve performance in this VM config if the
> > multifd transfer is enabled: the downtime performance with this commit
> > present is 1141 ms enabled / 1730 ms disabled.

[1]

> > 
> > Smaller VF counts actually do seem to benefit from this commit, so it's
> > likely that in the future adding some kind of a memslot pre-allocation
> > bit stream message might make sense to avoid this downtime regression for
> > 4 VF configs (and likely higher VF count too).

[...]

> I did a quick run of a VM with a mlx5 VF and a vGPU and I didn't see
> any issue when migrating. I used 4 channels for multifd. The trace
> events looked ok and useful. We will tune these with time. I wished
> we had some way to dump the thread and channel usage on each side.
> 
> A build was provided to RHEL QE. This to get more results when under
> stress and with larger device states. Don't expect feedback before
> next year though !
> 
> Having a small cookbook to run the migration from QEMU and from
> libvirt would be a plus.

Cédric,

Did you test also with commit 5504a8126115 and relevant patches reverted,
per mentioned above [1]?  Or vanilla master branch?

I wonder whether it shows the same regression in your setup.

Thanks,

-- 
Peter Xu