Re: [Xen-devel] [PATCH v3 2/3] Introduce migration precopy policy

[Jennifer Herbert <Jennifer.Herbert@xxxxxxxxxx>]

On 26/09/17 12:02, Andrew Cooper wrote:
> On 25/09/17 19:55, Jennifer Herbert wrote:
> > @@ -46,7 +60,22 @@ struct save_callbacks {
> >        */
> >       int (*suspend)(void* data);
> >   
> > -    /* Called after the guest's dirty pages have been
> > +    /*
> > +     * Called before and after every batch of page data sent during
> > +     * the precopy phase of a live migration to ask the caller what
> > +     * to do next based on the current state of the precopy migration.
> How is the callback supposed to determine whether it is before or ahead
> of the data batch?
>
> As far as I can tell, its not possible.
>
> ~Andrew
You look at the dirty_count.  It works well for me.
I can add that info to the comment.

-jenny

> > +     *
> > +     * Should return one of the values listed below:
> > +     */
> > +#define XGS_POLICY_ABORT          (-1) /* Abandon the migration entirely
> > +                                        * and tidy up. */
> > +#define XGS_POLICY_CONTINUE_PRECOPY 0  /* Remain in the precopy phase. */
> > +#define XGS_POLICY_STOP_AND_COPY    1  /* Immediately suspend and transmit the
> > +                                        * remaining dirty pages. */
> > +    precopy_policy_t precopy_policy;
> > +
> > +    /*
> > +     * Called after the guest's dirty pages have been
> >        *  copied into an output buffer.
> >        * Callback function resumes the guest & the device model,
> >        *  returns to xc_domain_save.

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