Re: [Qemu-devel] [PATCH 0/5] QEMU VFIO live migration

[Gonglei (Arei)]

> >
> > > -----Original Message-----
> > > From: Zhao Yan [mailto:address@hidden
> > > Sent: Thursday, February 21, 2019 10:05 AM
> > > To: Gonglei (Arei) <address@hidden>
> > > Cc: address@hidden; address@hidden;
> > > address@hidden; address@hidden;
> > > address@hidden; address@hidden; address@hidden;
> > > address@hidden; address@hidden;
> address@hidden;
> > > address@hidden; address@hidden; address@hidden;
> > > address@hidden; address@hidden; address@hidden;
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> address@hidden;
> > > address@hidden; address@hidden; address@hidden;
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> > > Subject: Re: [PATCH 0/5] QEMU VFIO live migration
> > >
> > > > >
> > > > > > 5) About log sync, why not register log_global_start/stop in
> > > > > vfio_memory_listener?
> > > > > >
> > > > > >
> > > > > seems log_global_start/stop cannot be iterately called in pre-copy
> phase?
> > > > > for dirty pages in system memory, it's better to transfer dirty data
> > > > > iteratively to reduce down time, right?
> > > > >
> > > >
> > > > We just need invoking only once for start and stop logging. Why we need
> to
> > > call
> > > > them literately? See memory_listener of vhost.
> > > >
> > > the dirty pages in system memory produces by device is incremental.
> > > if it can be got iteratively, the dirty pages in stop-and-copy phase can 
> > > be
> > > minimal.
> > > :)
> > >
> > I mean starting or stopping the capability of logging, not log sync.
> >
> > We register the below callbacks:
> >
> > .log_sync = vfio_log_sync,
> > .log_global_start = vfio_log_global_start,
> > .log_global_stop = vfio_log_global_stop,
> >
> .log_global_start is also a good point to notify logging state.
> But if notifying in .save_setup handler, we can do fine-grained
> control of when to notify of logging starting together with get_buffer
> operation.
> Is there any special benifit by registering to .log_global_start/stop?
> 

Performance benefit when one VM has multiple same vfio devices.


Regards,
-Gonglei