Re: [PATCH v2 2/3] Add zero-copy-copied migration stat

[Leonardo Brás]

Thanks Daniel, Markus and Dave for the feedback!

On Mon, 2022-07-04 at 14:14 +0100, Daniel P. Berrangé wrote:
> On Mon, Jul 04, 2022 at 02:59:50PM +0200, Markus Armbruster wrote:
> > Daniel P. Berrangé <berrange@redhat.com> writes:
> > 
> > > On Mon, Jul 04, 2022 at 02:04:41PM +0200, Markus Armbruster wrote:
> > 
[...]

> 
> since 7.1, unless you're planning for really tortuous review :)
> 

Ok, updated :)

> > [...]
> > 
> > > > Please rephrase the documentation of @zero-copy-copied in terms of
> > > > @dirty-sync-count.  Here's my attempt.
> > > > 
> > > > # @zero-copy-copied: Number of times dirty RAM synchronization could not
> > > > #                    avoid copying zero pages.  This is between 0 and
> > > > #                    @dirty-sync-count.  (since 7.1)

That's a great description! And it's almost 100% correct.

IIUC dirty-sync-count increments on migration_bitmap_sync() once after each full
dirty-bitmap scan, and even with multifd syncing at the same point, it could
potentially have a increment per multifd channel.

The only change would be having:
# This is between 0 and @dirty-sync-count * @multifd-channel.


> > > 
> > > Any one have preferences on the name - i get slight put off by the
> > > repeated word in the property name here.
> > > 
> > >    @zero-copy-rejects ?
> > >    @zero-copy-misses ?
> > >    @zero-copy-fails ?
> > 
> > I'd consider any of these an improvement.  Not a native speaker, but
> > perhaps "failures" instead of "fails".
> > 
> > We could also express the connection to @dirty-sync-count right in the
> > name, like @dirty-sync-rejected-zero-copy, @dirty-sync-missed-zero-copy,
> > @dirty-sync-failed-zero-copy.  Or maybe -copies.
> 
> Yeah, @dirty-sync-missed-zero-copy   is probably my favourite.

Ok then, this one there is :)

I will update my patchset with the suggestions, and I should publish a v3
shortly. 

Best regards,
Leo

> 
> With regards,
> Daniel