Re: [PATCH RESEND v6 0/5] migration: reduce time of loading non-iterable vmstate

[Peter Xu <peterx@redhat.com>]

On Wed, Mar 08, 2023 at 06:03:45AM -0800, Chuang Xu wrote:
> IIUC, Do you mean that different ways to get flatview are tricky?

Yes, and properly define when to use which.

> As you said, it's slightly beyond what this series does. Maybe it would be
> better if we discuss it in a new series and keep this series at v6?
> what's your take?

Quotting your test result:

                        time of loading non-iterable vmstate
before                                  112 ms
long's patch applied                    103 ms
my patch applied                         44 ms
both applied                             39 ms
add as_to_flat_rcu                       19 ms

If introducing address_space_to_flatview_rcu() can further half the time,
maybe still worth it?

The thing is the extra _rcu() doesn't bring the major complexity, IMHO.  It
brings some on identifying which is really safe to not reference a latest
flatview (it seems to me only during a commit() hook..).

The major complexity still comes from the nested enforced commit() during
address_space_to_flatview() but that is already in the patchset.

Thanks,

-- 
Peter Xu