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

[Chuang Xu]

Hi, Peter,

On 2023/3/8 下午11:46, Peter Xu wrote:
> > 1. squash fix into patch1 of yours.
> > 2. introduce address_space_to_flatview_rcu()
> > 3. add specific comment to define when to use which as_to_flat()
> This can be together with 2).
>
> We should suggest using address_space_to_flatview() by default in the
> comment, and only use _rcu() with cautions e.g. we can mention commit()
> hooks as example, and also mention the possibility of seeing very old (or
> purely empty flatview) if during vm load.  In that sense this can be the
> last patch of your set so there's the vm load context to reference.
>
> I hope there'll be no outliers that takes only RCU (no bql) but still
> expect a very new flatview then it'll crash easily if called in a vm load.
> But let's see..  I assume your test cases are already a much larger set so
> covers a lot of code paths already.
>
> > 4. Does enforce commit() need further modification or keep current status?
> >     Looks like you have some new thoughts on it?
> I don't.
>
> PS: I do have some thoughts but I don't think I mentioned them..  My
> thoughts were that we can actually avoid calling begin()/commit()/... hooks
> during a nested do_commit() at all but only update current_map.  That'll
> further avoid the _rcu() patch to be introduced, but I think that needs
> more changes and may not be necessary at all.  Ignore this.
Got it.

> > Are there any other missing points?
> No from my side.
>
> Note that 8.0 reached soft freeze.  Sorry to say so, but it seems this work
> will only be possible (if no further objections coming) for 8.1 merge
> windows, so the early merge will be after middle of Apirl.  Thanks for
> being consistent with it already so far.

I also want to thank you for your long-term guidance and suggestions for
this series.

To tell the truth, as a new comer, this is the first patch I try to send
to the community. Your active discussion in the emails makes me feel that
I am doing something really meaningful, so I am willing to continuously devote
my energy to participate in the discussion, and at the same time, I benefit
a lot from the discussion with you.

Thanks!