Re: [PATCH v4 3/7] migration/multifd: Implement ram_save_target_page_multifd to handle multifd version of MigrationOps::ram_save_target_page.

[Peter Xu]

On Sat, Mar 09, 2024 at 02:06:33AM +0000, hao.xiang@linux.dev wrote:
> > >  @@ -1122,10 +1122,6 @@ static int save_zero_page(RAMState *rs, 
> > > PageSearchStatus *pss,
> > >  QEMUFile *file = pss->pss_channel;
> > >  int len = 0;
> > >
> > >  - if (migrate_zero_page_detection() == ZERO_PAGE_DETECTION_NONE) {
> > >  - return 0;
> > >  - }
> > > 
> > >  We need to keep this to disable zero-page-detect on !multifd?
> 
> So if multifd is enabled, the new parameter takes effect. If multifd is
> not enabled, zero page checking will always be done in the main thread,
> which is exactly the behavior it is now. I thought legacy migration is a
> deprecated feature so I am trying to not add new stuff to it.

There's no plan to deprecate legacy migrations, I think there was a plan to
make multifd the default, but I don't yet think it all thorougly yet, and
even if it happens it doesn't mean we'll remove legacy migration code.

When repost please still make sure this parameter works for both multifd
and !multifd.

Thanks,

-- 
Peter Xu