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

[Markus Armbruster]

Leonardo Brás <leobras@redhat.com> writes:

> 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.

That's why we do patch review :)

> 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.

Makes sense to me.

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