Re: [PATCH v3 12/14] migration/multifd: Allow multifd sync without flush

[Peter Xu]

On Thu, Aug 01, 2024 at 09:35:14AM -0300, Fabiano Rosas wrote:
> Separate the multifd sync from flushing the client data to the
> channels. These two operations are closely related but not strictly
> necessary to be executed together.
> 
> The multifd sync is intrinsic to how multifd works. The multiple
> channels operate independently and may finish IO out of order in
> relation to each other. This applies also between the source and
> destination QEMU.
> 
> Flushing the data that is left in the client-owned data structures
> (e.g. MultiFDPages_t) prior to sync is usually the right thing to do,
> but that is particular to how the ram migration is implemented with
> several passes over dirty data.
> 
> Make these two routines separate, allowing future code to call the
> sync by itself if needed. This also allows the usage of
> multifd_ram_send to be isolated to ram code.

What's the usage of sync but not flush here?

-- 
Peter Xu