Re: [Qemu-devel] [PATCH 01/12] migration: Introduce announce parameters

[Dr. David Alan Gilbert]

* Vlad Yasevich (address@hidden) wrote:
> On 06/01/2017 03:02 AM, Jason Wang wrote:
> > 
> > 
> > On 2017年05月31日 02:57, Dr. David Alan Gilbert wrote:
> >> * Vlad Yasevich (address@hidden) wrote:
> >>> On 05/26/2017 12:03 AM, Jason Wang wrote:
> >>>> On 2017年05月25日 02:05, Vladislav Yasevich wrote:
> >>>>> Add parameters that control RARP/GARP announcement timeouts.
> >>>>> The parameters structure is added to the QAPI and a qmp command
> >>>>> is added to set/get the parameter data.
> >>>>>
> >>>>> Based on work by "Dr. David Alan Gilbert"<address@hidden>
> >>>>>
> >>>>> Signed-off-by: Vladislav Yasevich<address@hidden>
> >>>> I think it's better to explain e.g under which condition do we need to 
> >>>> tweak such
> >>>> parameters.
> >>>>
> >>>> Thanks
> >>>>
> >>> OK.  I'll rip off what dgilbert wrote in his original series for the 
> >>> description.
> >>>
> >>> Dave, if you have any text to add as to why migration might need to tweak 
> >>> this, I'd
> >>> appreciate it.
> >> Pretty much what I originally said;  that the existing values
> >> are arbitrary and fixed, and for systems with complex/sluggish
> >> network reconfiguration systems they can be too slow.
> >>
> >> Dave
> >>
> > 
> > I agree, but I'm not sure how much it can help in fact unless management 
> > can set
> > configuration specific parameters. And what we did here is best effort, 
> > there's no
> > guarantee that G(R)ARP packet can reach the destination.
> > 
> 
> So, that's what the series allows.  If management knows something new, it can 
> set
> appropriate parameter values.  Additionally, the management is also free to 
> trigger
> additional announcements through the new commands.
> 
> I am starting to think that just for the sake of migration, exposing 
> announce_self
> interface to management might be sufficient.  Management, when it deems 
> migration
> complete, may use the interface to trigger announcements in addition to 
> whatever
> best effort QEMU may attempt itself.
> 
> Dave, would that be enough, or do the parameters still make sense?

I'd still like to be able to set the parameters to be able to work
around the very broken setups that are out there.
The way I got to this point was a hack for a user where I just
increased it so it was doing about 10 seconds of announce which was long
enough for the network to get it's act together.

Dave

> Thanks
> -vlad
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK