Re: [PATCH 1/2] migration: Implement dirty ring

[Peter Xu]

Hi, Shota,

On Thu, Jun 20, 2024 at 06:47:13PM +0900, Shota Imamura wrote:
> This commit implements the dirty ring as an alternative dirty tracking
> method to the dirty bitmap.
> 
> While the dirty ring has already been implemented in accel/kvm using KVM's
> dirty ring, it was designed to set bits in the ramlist and ramblock bitmap.
> This commit introduces a new dirty ring to replace the bitmap, allowing the
> use of the dirty ring even without KVM. When using KVM's dirty ring, this
> implementation maximizes its effectiveness.

It looks like this patch will introduce a ring but still it keeps the
bitmaps around.

Could you elaborate your motivation of this work?  It'll be interesting to
know whether you did any kind of measurement around it.

> 
> To enable the dirty ring, specify the startup option
> "-migration dirty-logging=ring,dirty-ring-size=N". To use the bitmap,
> either specify nothing or "-migration dirty-logging=bitmap". If the dirty
> ring becomes full, it falls back to the bitmap for that round.

I remember adding such option is not suggested.  We may consider using
either QMP to setup a migration parameter, or something else.

Thanks,

-- 
Peter Xu