Re: [Qemu-devel] [v2 RESEND 0/4] Fix long vm downtime during live migration

[Paolo Bonzini]

On 02/11/2015 08:36, Liang Li wrote:
> The patch 3ea3b7fa9af067982f34b of kvm introduces a lazy collapsing
> of small sptes into large sptes mechanism, which intend to solve the
> performance drop issue if live migration fails or is canceled. The
> rmap will be scanned in the KVM_SET_USER_MEMORY_REGION ioctl context
> when dirty logging is stopped so as to drop the small sptes, scanning
> the rmap and drop the small sptes is a time consuming operation which
> will take dozens of milliseconds, the actual time depends on VM's
> memory size. For a VM with 8GB RAM, it will take about 30ms.

I'm okay with these patches.  Juan, can they be included in 2.5?

However, the KVM patch is a regression too.  Wanpeng, can you look into
doing the collapsing from a work item?

Thanks,

Paolo