Re: [External] Re: [PATCH v4 6/7] migration/multifd: Add zero pages and zero bytes counter to migration status interface.

[hao.xiang@linux.dev]

> 
> On Thu, Feb 29, 2024 at 11:40 PM Markus Armbruster <armbru@redhat.com> wrote:
> 
> > 
> > Hao Xiang <hao.xiang@bytedance.com> writes:
> > 
> >  This change extends the MigrationStatus interface to track zero pages
> > 
> >  and zero bytes counter.
> > 
> >  Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
> > 
> >  [...]
> > 
> >  diff --git a/qapi/migration.json b/qapi/migration.json
> > 
> >  index ca9561fbf1..03b850bab7 100644
> > 
> >  --- a/qapi/migration.json
> > 
> >  +++ b/qapi/migration.json
> > 
> >  @@ -63,6 +63,10 @@
> > 
> >  # between 0 and @dirty-sync-count * @multifd-channels. (since
> > 
> >  # 7.1)
> > 
> >  #
> > 
> >  +# @zero-pages: number of zero pages (since 9.0)
> > 
> >  +#
> > 
> >  +# @zero-bytes: number of zero bytes sent (since 9.0)
> > 
> >  +#
> > 
> >  Discussion of v3 has led me to believe:
> > 
> >  1. A page is either migrated as a normal page or as a zero page.
> > 
> >  2. The following equations hold:
> > 
> >  @normal-bytes = @normal * @page-size
> > 
> >  @zero-bytes = @zero-pages * @page-size
> > 
> >  3. @zero-pages is the same as @duplicate, with a better name. We intend
> > 
> >  to drop @duplicate eventually.
> > 
> >  If this is correct, I'd like you to
> > 
> >  A. Name it @zero for consistency with @normal. Disregard my advice to
> > 
> >  name it @zero-pages; two consistent bad names are better than one bad
> > 
> >  name, one good name, and inconsistency.
> > 
> >  B. Add @zero and @zero-bytes next to @normal and @normal-bytes.
> > 
> >  C. Deprecate @duplicate (item 3). Separate patch, please.
> > 
> >  D. Consider documenting more clearly what normal and zero pages are
> > 
> >  (item 1), and how @FOO, @FOO-pages and @page-size are related (item
> > 
> >  2). Could be done in a followup patch.

I will move this out of the current patchset and put them into a seperate patchset. I think I am not totally understanding the exact process of deprecating an interface and hence will need your help to probably go a few more versions. And I read from earlier conversation the soft release for QEMU9.0 is 3/12 so hopefully the rest of this patchset can catch it.

> > 
> >  # Features:
> > 
> >  #
> > 
> >  # @deprecated: Member @skipped is always zero since 1.5.3
> > 
> >  @@ -81,7 +85,8 @@
> > 
> >  'multifd-bytes': 'uint64', 'pages-per-second': 'uint64',
> > 
> >  'precopy-bytes': 'uint64', 'downtime-bytes': 'uint64',
> > 
> >  'postcopy-bytes': 'uint64',
> > 
> >  - 'dirty-sync-missed-zero-copy': 'uint64' } }
> > 
> >  + 'dirty-sync-missed-zero-copy': 'uint64',
> > 
> >  + 'zero-pages': 'int', 'zero-bytes': 'size' } }
> > 
> >  [...]
> >
>